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 $149.73   12.617%   $168.6214   $168.62   $168.60   $168.60  
  Purchase #2 $217.34   10.165%   $239.4326   $239.43   $239.45   $239.40  
  Purchase #3 $177.72   10.705%   $196.7449   $196.74   $196.75   $196.70  
  Purchase #4 $226.75   4.365%   $236.6476   $236.65   $236.65   $236.60  
  Purchase #5 $57.63   4.770%   $60.379   $60.38   $60.40   $60.40  
  Purchase #6 $44.69   12.590%   $50.3165   $50.32   $50.30   $50.30  
  Purchase #7 $140.53   8.141%   $151.9705   $151.97   $151.95   $152.00  
  7 purchase totals = $1,014.39       $1,104.1125   $1,104.11   $1,104.10   $1,104.00