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 $210.26   12.251%   $236.019   $236.02   $236.00   $236.00  
  Purchase #2 $76.67   5.669%   $81.0164   $81.02   $81.00   $81.00  
  Purchase #3 $121.85   12.597%   $137.1994   $137.20   $137.20   $137.20  
  Purchase #4 $85.64   6.515%   $91.2194   $91.22   $91.20   $91.20  
  Purchase #5 $97.74   7.556%   $105.1252   $105.13   $105.15   $105.10  
  Purchase #6 $238.89   13.245%   $270.531   $270.53   $270.55   $270.50  
  Purchase #7 $125.65   4.160%   $130.877   $130.88   $130.90   $130.90  
  7 purchase totals = $956.70       $1,051.9874   $1,052.00   $1,052.00   $1,051.90