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 $92.64   4.781%   $97.0691   $97.07   $97.05   $97.10  
  Purchase #2 $64.66   4.129%   $67.3298   $67.33   $67.35   $67.30  
  Purchase #3 $191.79   6.171%   $203.6254   $203.63   $203.65   $203.60  
  Purchase #4 $45.33   9.106%   $49.4577   $49.46   $49.45   $49.50  
  Purchase #5 $49.60   5.686%   $52.4203   $52.42   $52.40   $52.40  
  Purchase #6 $245.34   3.598%   $254.1673   $254.17   $254.15   $254.20  
  Purchase #7 $219.81   4.509%   $229.7212   $229.72   $229.70   $229.70  
  7 purchase totals = $909.17       $953.7908   $953.80   $953.75   $953.80