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 $88.87   8.794%   $96.6852   $96.69   $96.70   $96.70  
  Purchase #2 $101.37   3.162%   $104.5753   $104.58   $104.60   $104.60  
  Purchase #3 $76.58   9.254%   $83.6667   $83.67   $83.65   $83.70  
  Purchase #4 $177.69   5.795%   $187.9871   $187.99   $188.00   $188.00  
  Purchase #5 $133.90   13.249%   $151.6404   $151.64   $151.65   $151.60  
  Purchase #6 $245.33   4.462%   $256.2766   $256.28   $256.30   $256.30  
  Purchase #7 $199.45   11.132%   $221.6528   $221.65   $221.65   $221.70  
  7 purchase totals = $1,023.19       $1,102.4841   $1,102.50   $1,102.55   $1,102.60