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 $86.42   10.213%   $95.2461   $95.25   $95.25   $95.20  
  Purchase #2 $140.53   10.164%   $154.8135   $154.81   $154.80   $154.80  
  Purchase #3 $229.78   8.637%   $249.6261   $249.63   $249.65   $249.60  
  Purchase #4 $64.88   9.535%   $71.0663   $71.07   $71.05   $71.10  
  Purchase #5 $171.36   7.810%   $184.7432   $184.74   $184.75   $184.70  
  Purchase #6 $241.46   10.670%   $267.2238   $267.22   $267.20   $267.20  
  Purchase #7 $214.56   10.268%   $236.591   $236.59   $236.60   $236.60  
  7 purchase totals = $1,148.99       $1,259.3100   $1,259.31   $1,259.30   $1,259.20