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 $88.49   7.510%   $95.1356   $95.14   $95.15   $95.10  
  Purchase #2 $244.42   6.652%   $260.6788   $260.68   $260.70   $260.70  
  Purchase #3 $112.67   5.690%   $119.0809   $119.08   $119.10   $119.10  
  Purchase #4 $161.41   10.421%   $178.2305   $178.23   $178.25   $178.20  
  Purchase #5 $74.35   5.356%   $78.3322   $78.33   $78.35   $78.30  
  Purchase #6 $116.25   8.827%   $126.5114   $126.51   $126.50   $126.50  
  Purchase #7 $229.65   13.672%   $261.0477   $261.05   $261.05   $261.00  
  7 purchase totals = $1,027.24       $1,119.0171   $1,119.02   $1,119.10   $1,118.90