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 $195.37   11.340%   $217.525   $217.53   $217.55   $217.50  
  Purchase #2 $140.99   12.416%   $158.4953   $158.50   $158.50   $158.50  
  Purchase #3 $53.96   9.587%   $59.1331   $59.13   $59.15   $59.10  
  Purchase #4 $236.92   13.180%   $268.1461   $268.15   $268.15   $268.10  
  Purchase #5 $64.45   7.569%   $69.3282   $69.33   $69.35   $69.30  
  Purchase #6 $58.25   13.768%   $66.2699   $66.27   $66.25   $66.30  
  Purchase #7 $190.41   7.572%   $204.8278   $204.83   $204.85   $204.80  
  7 purchase totals = $940.35       $1,043.7254   $1,043.74   $1,043.80   $1,043.60