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 $92.69   4.478%   $96.8407   $96.84   $96.85   $96.80  
  Purchase #2 $208.78   13.574%   $237.1198   $237.12   $237.10   $237.10  
  Purchase #3 $146.76   3.335%   $151.6544   $151.65   $151.65   $151.70  
  Purchase #4 $76.41   11.562%   $85.2445   $85.24   $85.25   $85.20  
  Purchase #5 $209.29   8.809%   $227.7264   $227.73   $227.75   $227.70  
  Purchase #6 $244.69   11.446%   $272.6972   $272.70   $272.70   $272.70  
  Purchase #7 $29.71   3.212%   $30.6643   $30.66   $30.65   $30.70  
  7 purchase totals = $1,008.33       $1,101.9473   $1,101.94   $1,101.95   $1,101.90