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 $59.43   4.867%   $62.3225   $62.32   $62.30   $62.30  
  Purchase #2 $169.87   9.686%   $186.3236   $186.32   $186.30   $186.30  
  Purchase #3 $172.29   8.688%   $187.2586   $187.26   $187.25   $187.30  
  Purchase #4 $69.38   7.258%   $74.4156   $74.42   $74.40   $74.40  
  Purchase #5 $102.80   7.744%   $110.7608   $110.76   $110.75   $110.80  
  Purchase #6 $232.64   5.295%   $244.9583   $244.96   $244.95   $245.00  
  Purchase #7 $79.57   10.279%   $87.749   $87.75   $87.75   $87.70  
  7 purchase totals = $885.98       $953.7884   $953.79   $953.70   $953.80