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 $32.68   9.137%   $35.666   $35.67   $35.65   $35.70  
  Purchase #2 $226.64   11.669%   $253.0866   $253.09   $253.10   $253.10  
  Purchase #3 $45.47   6.531%   $48.4396   $48.44   $48.45   $48.40  
  Purchase #4 $9.81   3.340%   $10.1377   $10.14   $10.15   $10.10  
  Purchase #5 $10.92   8.817%   $11.8828   $11.88   $11.90   $11.90  
  Purchase #6 $214.53   3.851%   $222.7916   $222.79   $222.80   $222.80  
  Purchase #7 $106.96   11.651%   $119.4219   $119.42   $119.40   $119.40  
  7 purchase totals = $647.01       $701.4262   $701.43   $701.45   $701.40