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 $59.37   7.681%   $63.9302   $63.93   $63.95   $63.90  
  Purchase #2 $228.27   9.806%   $250.6542   $250.65   $250.65   $250.70  
  Purchase #3 $206.87   10.433%   $228.4527   $228.45   $228.45   $228.50  
  Purchase #4 $189.63   9.525%   $207.6923   $207.69   $207.70   $207.70  
  Purchase #5 $152.81   4.251%   $159.306   $159.31   $159.30   $159.30  
  Purchase #6 $154.38   12.374%   $173.483   $173.48   $173.50   $173.50  
  Purchase #7 $119.55   5.359%   $125.9567   $125.96   $125.95   $126.00  
  7 purchase totals = $1,110.88       $1,209.4751   $1,209.47   $1,209.50   $1,209.60