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 $177.61   13.142%   $200.9515   $200.95   $200.95   $201.00  
  Purchase #2 $131.97   5.548%   $139.2917   $139.29   $139.30   $139.30  
  Purchase #3 $146.79   4.830%   $153.88   $153.88   $153.90   $153.90  
  Purchase #4 $171.71   13.738%   $195.2995   $195.30   $195.30   $195.30  
  Purchase #5 $169.33   10.490%   $187.0927   $187.09   $187.10   $187.10  
  Purchase #6 $105.26   13.555%   $119.528   $119.53   $119.55   $119.50  
  Purchase #7 $59.27   12.158%   $66.476   $66.48   $66.50   $66.50  
  7 purchase totals = $961.94       $1,062.5194   $1,062.52   $1,062.60   $1,062.60