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 $49.87   5.396%   $52.561   $52.56   $52.55   $52.60  
  Purchase #2 $153.34   5.757%   $162.1678   $162.17   $162.15   $162.20  
  Purchase #3 $195.55   10.242%   $215.5782   $215.58   $215.60   $215.60  
  Purchase #4 $109.48   6.516%   $116.6137   $116.61   $116.60   $116.60  
  Purchase #5 $5.82   12.442%   $6.5441   $6.54   $6.55   $6.50  
  Purchase #6 $187.81   3.754%   $194.8604   $194.86   $194.85   $194.90  
  Purchase #7 $168.71   9.466%   $184.6801   $184.68   $184.70   $184.70  
  7 purchase totals = $870.58       $933.0053   $933.00   $933.00   $933.10