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 $109.42   3.827%   $113.6075   $113.61   $113.60   $113.60  
  Purchase #2 $208.32   4.334%   $217.3486   $217.35   $217.35   $217.30  
  Purchase #3 $43.78   6.323%   $46.5482   $46.55   $46.55   $46.50  
  Purchase #4 $190.75   13.339%   $216.1941   $216.19   $216.20   $216.20  
  Purchase #5 $55.39   6.443%   $58.9588   $58.96   $58.95   $59.00  
  Purchase #6 $70.52   6.522%   $75.1193   $75.12   $75.10   $75.10  
  Purchase #7 $137.83   7.182%   $147.729   $147.73   $147.75   $147.70  
  7 purchase totals = $816.01       $875.5055   $875.51   $875.50   $875.40