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 $58.46   4.804%   $61.2684   $61.27   $61.25   $61.30  
  Purchase #2 $232.97   13.743%   $264.9871   $264.99   $265.00   $265.00  
  Purchase #3 $197.35   7.538%   $212.2262   $212.23   $212.25   $212.20  
  Purchase #4 $26.71   3.406%   $27.6197   $27.62   $27.60   $27.60  
  Purchase #5 $189.27   10.499%   $209.1415   $209.14   $209.15   $209.10  
  Purchase #6 $227.94   9.639%   $249.9111   $249.91   $249.90   $249.90  
  Purchase #7 $150.89   6.846%   $161.2199   $161.22   $161.20   $161.20  
  7 purchase totals = $1,083.59       $1,186.3739   $1,186.38   $1,186.35   $1,186.30