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 $82.72   6.581%   $88.1638   $88.16   $88.15   $88.20  
  Purchase #2 $212.94   11.134%   $236.6487   $236.65   $236.65   $236.60  
  Purchase #3 $195.39   5.294%   $205.7339   $205.73   $205.75   $205.70  
  Purchase #4 $159.77   11.720%   $178.495   $178.50   $178.50   $178.50  
  Purchase #5 $161.41   6.267%   $171.5256   $171.53   $171.55   $171.50  
  Purchase #6 $95.56   10.253%   $105.3578   $105.36   $105.35   $105.40  
  Purchase #7 $136.65   10.589%   $151.1199   $151.12   $151.10   $151.10  
  7 purchase totals = $1,044.44       $1,137.0447   $1,137.05   $1,137.05   $1,137.00