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 $87.56   5.234%   $92.1429   $92.14   $92.15   $92.10  
  Purchase #2 $205.86   7.428%   $221.1513   $221.15   $221.15   $221.20  
  Purchase #3 $176.50   12.102%   $197.86   $197.86   $197.85   $197.90  
  Purchase #4 $101.64   8.810%   $110.5945   $110.59   $110.60   $110.60  
  Purchase #5 $70.84   4.863%   $74.2849   $74.28   $74.30   $74.30  
  Purchase #6 $204.55   7.374%   $219.6335   $219.63   $219.65   $219.60  
  Purchase #7 $85.69   8.338%   $92.8348   $92.83   $92.85   $92.80  
  7 purchase totals = $932.64       $1,008.5019   $1,008.48   $1,008.55   $1,008.50