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 $95.59   6.655%   $101.9515   $101.95   $101.95   $102.00  
  Purchase #2 $80.58   5.574%   $85.0715   $85.07   $85.05   $85.10  
  Purchase #3 $205.39   4.566%   $214.7681   $214.77   $214.75   $214.80  
  Purchase #4 $116.45   6.307%   $123.7945   $123.79   $123.80   $123.80  
  Purchase #5 $56.70   11.370%   $63.1468   $63.15   $63.15   $63.10  
  Purchase #6 $158.29   8.507%   $171.7557   $171.76   $171.75   $171.80  
  Purchase #7 $222.33   4.540%   $232.4238   $232.42   $232.40   $232.40  
  7 purchase totals = $935.33       $992.9119   $992.91   $992.85   $993.00