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 $58.93   4.650%   $61.6702   $61.67   $61.65   $61.70  
  Purchase #2 $84.59   12.544%   $95.201   $95.20   $95.20   $95.20  
  Purchase #3 $246.47   4.127%   $256.6418   $256.64   $256.65   $256.60  
  Purchase #4 $88.71   4.495%   $92.6975   $92.70   $92.70   $92.70  
  Purchase #5 $21.97   6.589%   $23.4176   $23.42   $23.40   $23.40  
  Purchase #6 $8.56   10.419%   $9.4519   $9.45   $9.45   $9.50  
  Purchase #7 $209.81   11.406%   $233.7409   $233.74   $233.75   $233.70  
  7 purchase totals = $719.04       $772.8209   $772.82   $772.80   $772.80