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 $188.96   11.445%   $210.5865   $210.59   $210.60   $210.60  
  Purchase #2 $54.46   11.861%   $60.9195   $60.92   $60.90   $60.90  
  Purchase #3 $87.36   8.165%   $94.4929   $94.49   $94.50   $94.50  
  Purchase #4 $195.68   10.510%   $216.246   $216.25   $216.25   $216.20  
  Purchase #5 $58.63   3.134%   $60.4675   $60.47   $60.45   $60.50  
  Purchase #6 $174.66   4.237%   $182.0603   $182.06   $182.05   $182.10  
  Purchase #7 $209.96   4.254%   $218.8917   $218.89   $218.90   $218.90  
  7 purchase totals = $969.71       $1,043.6644   $1,043.67   $1,043.65   $1,043.70