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 $59.94   4.553%   $62.6691   $62.67   $62.65   $62.70  
  Purchase #2 $24.71   5.171%   $25.9878   $25.99   $26.00   $26.00  
  Purchase #3 $135.88   3.206%   $140.2363   $140.24   $140.25   $140.20  
  Purchase #4 $210.29   3.280%   $217.1875   $217.19   $217.20   $217.20  
  Purchase #5 $13.54   9.837%   $14.8719   $14.87   $14.85   $14.90  
  Purchase #6 $35.56   3.420%   $36.7762   $36.78   $36.80   $36.80  
  Purchase #7 $191.99   13.627%   $218.1525   $218.15   $218.15   $218.20  
  7 purchase totals = $671.91       $715.8813   $715.89   $715.90   $716.00