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 $95.52   8.618%   $103.7519   $103.75   $103.75   $103.80  
  Purchase #2 $14.85   8.823%   $16.1602   $16.16   $16.15   $16.20  
  Purchase #3 $77.62   4.583%   $81.1773   $81.18   $81.20   $81.20  
  Purchase #4 $201.33   5.104%   $211.6059   $211.61   $211.60   $211.60  
  Purchase #5 $39.25   8.625%   $42.6353   $42.64   $42.65   $42.60  
  Purchase #6 $221.47   13.636%   $251.6696   $251.67   $251.65   $251.70  
  Purchase #7 $43.35   5.869%   $45.8942   $45.89   $45.90   $45.90  
  7 purchase totals = $693.39       $752.8944   $752.90   $752.90   $753.00