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 $175.64   11.165%   $195.2502   $195.25   $195.25   $195.30  
  Purchase #2 $207.84   11.830%   $232.4275   $232.43   $232.45   $232.40  
  Purchase #3 $169.93   13.644%   $193.1152   $193.12   $193.10   $193.10  
  Purchase #4 $51.37   8.821%   $55.9013   $55.90   $55.90   $55.90  
  Purchase #5 $186.92   6.871%   $199.7633   $199.76   $199.75   $199.80  
  Purchase #6 $118.89   5.650%   $125.6073   $125.61   $125.60   $125.60  
  Purchase #7 $26.69   9.678%   $29.2731   $29.27   $29.25   $29.30  
  7 purchase totals = $937.28       $1,031.3379   $1,031.34   $1,031.30   $1,031.40