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 $72.76   4.716%   $76.1914   $76.19   $76.20   $76.20  
  Purchase #2 $96.46   5.155%   $101.4325   $101.43   $101.45   $101.40  
  Purchase #3 $66.92   8.571%   $72.6557   $72.66   $72.65   $72.70  
  Purchase #4 $220.93   5.360%   $232.7718   $232.77   $232.75   $232.80  
  Purchase #5 $240.32   3.614%   $249.0052   $249.01   $249.00   $249.00  
  Purchase #6 $58.47   9.361%   $63.9434   $63.94   $63.95   $63.90  
  Purchase #7 $202.57   12.618%   $228.1303   $228.13   $228.15   $228.10  
  7 purchase totals = $958.43       $1,024.1303   $1,024.13   $1,024.15   $1,024.10