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 $175.94   11.377%   $195.9567   $195.96   $195.95   $196.00  
  Purchase #2 $245.41   3.399%   $253.7515   $253.75   $253.75   $253.80  
  Purchase #3 $43.76   12.139%   $49.072   $49.07   $49.05   $49.10  
  Purchase #4 $75.66   10.789%   $83.823   $83.82   $83.80   $83.80  
  Purchase #5 $201.94   5.124%   $212.2874   $212.29   $212.30   $212.30  
  Purchase #6 $20.31   9.454%   $22.2301   $22.23   $22.25   $22.20  
  Purchase #7 $131.96   3.429%   $136.4849   $136.48   $136.50   $136.50  
  7 purchase totals = $894.98       $953.6056   $953.60   $953.60   $953.70