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 $35.75   4.160%   $37.2372   $37.24   $37.25   $37.20  
  Purchase #2 $200.64   9.158%   $219.0146   $219.01   $219.00   $219.00  
  Purchase #3 $235.63   11.584%   $262.9254   $262.93   $262.95   $262.90  
  Purchase #4 $118.66   13.694%   $134.9093   $134.91   $134.90   $134.90  
  Purchase #5 $182.29   12.439%   $204.9651   $204.97   $204.95   $205.00  
  Purchase #6 $101.84   9.718%   $111.7368   $111.74   $111.75   $111.70  
  Purchase #7 $190.92   8.431%   $207.0165   $207.02   $207.00   $207.00  
  7 purchase totals = $1,065.73       $1,177.8049   $1,177.82   $1,177.80   $1,177.70