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 $103.95   7.766%   $112.0228   $112.02   $112.00   $112.00  
  Purchase #2 $213.29   12.223%   $239.3604   $239.36   $239.35   $239.40  
  Purchase #3 $213.59   10.780%   $236.615   $236.62   $236.60   $236.60  
  Purchase #4 $65.78   13.850%   $74.8905   $74.89   $74.90   $74.90  
  Purchase #5 $94.45   4.553%   $98.7503   $98.75   $98.75   $98.80  
  Purchase #6 $244.69   9.556%   $268.0726   $268.07   $268.05   $268.10  
  Purchase #7 $80.85   4.757%   $84.696   $84.70   $84.70   $84.70  
  7 purchase totals = $1,016.60       $1,114.4076   $1,114.41   $1,114.35   $1,114.50