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 $41.49   12.766%   $46.7866   $46.79   $46.80   $46.80  
  Purchase #2 $192.82   6.645%   $205.6329   $205.63   $205.65   $205.60  
  Purchase #3 $152.66   5.809%   $161.528   $161.53   $161.55   $161.50  
  Purchase #4 $204.63   9.719%   $224.518   $224.52   $224.50   $224.50  
  Purchase #5 $133.79   8.708%   $145.4404   $145.44   $145.45   $145.40  
  Purchase #6 $207.97   3.207%   $214.6396   $214.64   $214.65   $214.60  
  Purchase #7 $126.64   8.354%   $137.2195   $137.22   $137.20   $137.20  
  7 purchase totals = $1,060.00       $1,135.7650   $1,135.77   $1,135.80   $1,135.60