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 $22.98   5.305%   $24.1991   $24.20   $24.20   $24.20  
  Purchase #2 $221.94   10.255%   $244.6999   $244.70   $244.70   $244.70  
  Purchase #3 $117.98   9.433%   $129.1091   $129.11   $129.10   $129.10  
  Purchase #4 $103.83   4.648%   $108.656   $108.66   $108.65   $108.70  
  Purchase #5 $112.65   7.716%   $121.3421   $121.34   $121.35   $121.30  
  Purchase #6 $89.80   5.447%   $94.6914   $94.69   $94.70   $94.70  
  Purchase #7 $35.52   10.526%   $39.2588   $39.26   $39.25   $39.30  
  7 purchase totals = $704.70       $761.9564   $761.96   $761.95   $762.00