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 $84.55   13.131%   $95.6523   $95.65   $95.65   $95.70  
  Purchase #2 $151.67   8.741%   $164.9275   $164.93   $164.95   $164.90  
  Purchase #3 $140.67   7.315%   $150.96   $150.96   $150.95   $151.00  
  Purchase #4 $80.73   9.521%   $88.4163   $88.42   $88.40   $88.40  
  Purchase #5 $234.74   6.828%   $250.768   $250.77   $250.75   $250.80  
  Purchase #6 $207.42   13.584%   $235.5959   $235.60   $235.60   $235.60  
  Purchase #7 $122.75   5.354%   $129.322   $129.32   $129.30   $129.30  
  7 purchase totals = $1,022.53       $1,115.6420   $1,115.65   $1,115.60   $1,115.70