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 $116.89   8.630%   $126.9776   $126.98   $127.00   $127.00  
  Purchase #2 $211.91   7.268%   $227.3116   $227.31   $227.30   $227.30  
  Purchase #3 $236.55   5.593%   $249.7802   $249.78   $249.80   $249.80  
  Purchase #4 $57.78   4.285%   $60.2559   $60.26   $60.25   $60.30  
  Purchase #5 $138.29   11.700%   $154.4699   $154.47   $154.45   $154.50  
  Purchase #6 $186.93   4.492%   $195.3269   $195.33   $195.35   $195.30  
  Purchase #7 $202.87   10.425%   $224.0192   $224.02   $224.00   $224.00  
  7 purchase totals = $1,151.22       $1,238.1413   $1,238.15   $1,238.15   $1,238.20