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 $231.77   13.117%   $262.1713   $262.17   $262.15   $262.20  
  Purchase #2 $25.92   6.149%   $27.5138   $27.51   $27.50   $27.50  
  Purchase #3 $155.97   5.602%   $164.7074   $164.71   $164.70   $164.70  
  Purchase #4 $160.77   4.212%   $167.5416   $167.54   $167.55   $167.50  
  Purchase #5 $211.38   12.204%   $237.1768   $237.18   $237.20   $237.20  
  Purchase #6 $96.78   11.304%   $107.72   $107.72   $107.70   $107.70  
  Purchase #7 $194.42   3.355%   $200.9428   $200.94   $200.95   $200.90  
  7 purchase totals = $1,077.01       $1,167.7737   $1,167.77   $1,167.75   $1,167.70