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 $182.65   7.171%   $195.7478   $195.75   $195.75   $195.70  
  Purchase #2 $11.79   13.545%   $13.387   $13.39   $13.40   $13.40  
  Purchase #3 $108.40   12.602%   $122.0606   $122.06   $122.05   $122.10  
  Purchase #4 $206.62   3.835%   $214.5439   $214.54   $214.55   $214.50  
  Purchase #5 $31.85   9.734%   $34.9503   $34.95   $34.95   $35.00  
  Purchase #6 $132.95   13.590%   $151.0179   $151.02   $151.00   $151.00  
  Purchase #7 $187.80   8.332%   $203.4475   $203.45   $203.45   $203.40  
  7 purchase totals = $862.06       $935.1550   $935.16   $935.15   $935.10