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 $42.40   10.293%   $46.7642   $46.76   $46.75   $46.80  
  Purchase #2 $205.54   11.349%   $228.8667   $228.87   $228.85   $228.90  
  Purchase #3 $184.28   4.760%   $193.0517   $193.05   $193.05   $193.10  
  Purchase #4 $123.41   10.437%   $136.2903   $136.29   $136.30   $136.30  
  Purchase #5 $244.47   10.742%   $270.731   $270.73   $270.75   $270.70  
  Purchase #6 $199.98   11.486%   $222.9497   $222.95   $222.95   $222.90  
  Purchase #7 $24.68   11.470%   $27.5108   $27.51   $27.50   $27.50  
  7 purchase totals = $1,024.76       $1,126.1644   $1,126.16   $1,126.15   $1,126.20