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 $217.47   6.565%   $231.7469   $231.75   $231.75   $231.70  
  Purchase #2 $218.64   7.278%   $234.5526   $234.55   $234.55   $234.60  
  Purchase #3 $65.72   12.723%   $74.0816   $74.08   $74.10   $74.10  
  Purchase #4 $235.84   11.220%   $262.3012   $262.30   $262.30   $262.30  
  Purchase #5 $202.37   12.105%   $226.8669   $226.87   $226.85   $226.90  
  Purchase #6 $38.80   6.565%   $41.3472   $41.35   $41.35   $41.30  
  Purchase #7 $119.68   3.579%   $123.9633   $123.96   $123.95   $124.00  
  7 purchase totals = $1,098.52       $1,194.8597   $1,194.86   $1,194.85   $1,194.90