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 $40.60   8.795%   $44.1708   $44.17   $44.15   $44.20  
  Purchase #2 $95.99   8.297%   $103.9543   $103.95   $103.95   $104.00  
  Purchase #3 $87.69   11.676%   $97.9287   $97.93   $97.95   $97.90  
  Purchase #4 $150.81   6.327%   $160.3517   $160.35   $160.35   $160.40  
  Purchase #5 $164.63   6.286%   $174.9786   $174.98   $175.00   $175.00  
  Purchase #6 $244.49   13.383%   $277.2101   $277.21   $277.20   $277.20  
  Purchase #7 $243.63   5.802%   $257.7654   $257.77   $257.75   $257.80  
  7 purchase totals = $1,027.84       $1,116.3596   $1,116.36   $1,116.35   $1,116.50