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 $117.38   7.374%   $126.0356   $126.04   $126.05   $126.00  
  Purchase #2 $235.27   6.863%   $251.4166   $251.42   $251.40   $251.40  
  Purchase #3 $26.27   8.207%   $28.426   $28.43   $28.45   $28.40  
  Purchase #4 $36.43   13.449%   $41.3295   $41.33   $41.35   $41.30  
  Purchase #5 $86.69   8.802%   $94.3205   $94.32   $94.30   $94.30  
  Purchase #6 $209.42   11.593%   $233.6981   $233.70   $233.70   $233.70  
  Purchase #7 $218.92   11.393%   $243.8616   $243.86   $243.85   $243.90  
  7 purchase totals = $930.38       $1,019.0879   $1,019.10   $1,019.10   $1,019.00