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 $35.95   7.559%   $38.6675   $38.67   $38.65   $38.70  
  Purchase #2 $94.57   3.243%   $97.6369   $97.64   $97.65   $97.60  
  Purchase #3 $12.97   9.173%   $14.1597   $14.16   $14.15   $14.20  
  Purchase #4 $223.91   13.777%   $254.7581   $254.76   $254.75   $254.80  
  Purchase #5 $107.83   9.825%   $118.4243   $118.42   $118.40   $118.40  
  Purchase #6 $152.26   7.589%   $163.815   $163.82   $163.80   $163.80  
  Purchase #7 $66.89   9.842%   $73.4733   $73.47   $73.45   $73.50  
  7 purchase totals = $694.38       $760.9348   $760.94   $760.85   $761.00