Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $225.76   3.211%   $233.0092   $233.01   $233.00   $233.00  
  Purchase #2 $207.51   13.347%   $235.2064   $235.21   $235.20   $235.20  
  Purchase #3 $164.76   12.865%   $185.9564   $185.96   $185.95   $186.00  
  Purchase #4 $218.72   11.342%   $243.5272   $243.53   $243.55   $243.50  
  Purchase #5 $165.80   13.460%   $188.1167   $188.12   $188.10   $188.10  
  Purchase #6 $158.52   10.421%   $175.0394   $175.04   $175.05   $175.00  
  Purchase #7 $168.68   7.159%   $180.7558   $180.76   $180.75   $180.80  
  7 purchase totals = $1,309.75       $1,441.6111   $1,441.63   $1,441.60   $1,441.60