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 $116.53   7.786%   $125.603   $125.60   $125.60   $125.60  
  Purchase #2 $249.98   5.866%   $264.6438   $264.64   $264.65   $264.60  
  Purchase #3 $212.83   11.166%   $236.5946   $236.59   $236.60   $236.60  
  Purchase #4 $202.34   10.403%   $223.3894   $223.39   $223.40   $223.40  
  Purchase #5 $216.97   7.105%   $232.3857   $232.39   $232.40   $232.40  
  Purchase #6 $60.70   11.473%   $67.6641   $67.66   $67.65   $67.70  
  Purchase #7 $11.26   6.672%   $12.0113   $12.01   $12.00   $12.00  
  7 purchase totals = $1,070.61       $1,162.2919   $1,162.28   $1,162.30   $1,162.30