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 $114.90   3.585%   $119.0192   $119.02   $119.00   $119.00  
  Purchase #2 $196.56   8.686%   $213.6332   $213.63   $213.65   $213.60  
  Purchase #3 $41.32   13.653%   $46.9614   $46.96   $46.95   $47.00  
  Purchase #4 $245.59   10.713%   $271.9001   $271.90   $271.90   $271.90  
  Purchase #5 $91.41   3.167%   $94.305   $94.31   $94.30   $94.30  
  Purchase #6 $101.36   11.432%   $112.9475   $112.95   $112.95   $112.90  
  Purchase #7 $142.84   6.612%   $152.2846   $152.28   $152.30   $152.30  
  7 purchase totals = $933.98       $1,011.0510   $1,011.05   $1,011.05   $1,011.00