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 $185.68   8.761%   $201.9474   $201.95   $201.95   $201.90  
  Purchase #2 $49.77   13.394%   $56.4362   $56.44   $56.45   $56.40  
  Purchase #3 $99.59   10.668%   $110.2143   $110.21   $110.20   $110.20  
  Purchase #4 $59.41   8.446%   $64.4278   $64.43   $64.45   $64.40  
  Purchase #5 $119.63   11.377%   $133.2403   $133.24   $133.25   $133.20  
  Purchase #6 $183.39   3.174%   $189.2108   $189.21   $189.20   $189.20  
  Purchase #7 $14.75   10.773%   $16.339   $16.34   $16.35   $16.30  
  7 purchase totals = $712.22       $771.8158   $771.82   $771.85   $771.60