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 $59.67   4.331%   $62.2543   $62.25   $62.25   $62.30  
  Purchase #2 $236.88   13.201%   $268.1505   $268.15   $268.15   $268.20  
  Purchase #3 $180.96   11.203%   $201.2329   $201.23   $201.25   $201.20  
  Purchase #4 $11.37   9.276%   $12.4247   $12.42   $12.40   $12.40  
  Purchase #5 $146.35   5.325%   $154.1431   $154.14   $154.15   $154.10  
  Purchase #6 $64.39   11.319%   $71.6783   $71.68   $71.70   $71.70  
  Purchase #7 $15.97   11.697%   $17.838   $17.84   $17.85   $17.80  
  7 purchase totals = $715.59       $787.7218   $787.71   $787.75   $787.70