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 $67.63   9.360%   $73.9602   $73.96   $73.95   $74.00  
  Purchase #2 $124.84   7.251%   $133.8921   $133.89   $133.90   $133.90  
  Purchase #3 $109.73   8.553%   $119.1152   $119.12   $119.10   $119.10  
  Purchase #4 $235.35   12.770%   $265.4042   $265.40   $265.40   $265.40  
  Purchase #5 $206.55   4.609%   $216.0699   $216.07   $216.05   $216.10  
  Purchase #6 $18.66   10.157%   $20.5553   $20.56   $20.55   $20.60  
  Purchase #7 $209.96   5.781%   $222.0978   $222.10   $222.10   $222.10  
  7 purchase totals = $972.72       $1,051.0947   $1,051.10   $1,051.05   $1,051.20