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 $219.26   7.228%   $235.1081   $235.11   $235.10   $235.10  
  Purchase #2 $155.43   13.315%   $176.1255   $176.13   $176.15   $176.10  
  Purchase #3 $12.85   12.692%   $14.4809   $14.48   $14.50   $14.50  
  Purchase #4 $203.30   6.598%   $216.7137   $216.71   $216.70   $216.70  
  Purchase #5 $196.89   8.294%   $213.2201   $213.22   $213.20   $213.20  
  Purchase #6 $249.73   6.292%   $265.443   $265.44   $265.45   $265.40  
  Purchase #7 $154.27   12.512%   $173.5723   $173.57   $173.55   $173.60  
  7 purchase totals = $1,191.73       $1,294.6636   $1,294.66   $1,294.65   $1,294.60