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 $71.57   5.213%   $75.3009   $75.30   $75.30   $75.30  
  Purchase #2 $155.29   3.311%   $160.4317   $160.43   $160.45   $160.40  
  Purchase #3 $241.61   5.453%   $254.785   $254.79   $254.80   $254.80  
  Purchase #4 $68.81   10.604%   $76.1066   $76.11   $76.10   $76.10  
  Purchase #5 $243.62   5.321%   $256.583   $256.58   $256.60   $256.60  
  Purchase #6 $159.37   3.151%   $164.3917   $164.39   $164.40   $164.40  
  Purchase #7 $222.93   6.677%   $237.815   $237.82   $237.80   $237.80  
  7 purchase totals = $1,163.20       $1,225.4139   $1,225.42   $1,225.45   $1,225.40