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 $69.95   9.333%   $76.4784   $76.48   $76.50   $76.50  
  Purchase #2 $58.65   5.192%   $61.6951   $61.70   $61.70   $61.70  
  Purchase #3 $81.46   7.445%   $87.5247   $87.52   $87.50   $87.50  
  Purchase #4 $86.34   10.252%   $95.1916   $95.19   $95.20   $95.20  
  Purchase #5 $116.97   7.482%   $125.7217   $125.72   $125.70   $125.70  
  Purchase #6 $238.95   7.486%   $256.8378   $256.84   $256.85   $256.80  
  Purchase #7 $99.69   5.203%   $104.8769   $104.88   $104.90   $104.90  
  7 purchase totals = $752.01       $808.3262   $808.33   $808.35   $808.30