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 $205.33   9.671%   $225.1875   $225.19   $225.20   $225.20  
  Purchase #2 $224.80   13.516%   $255.184   $255.18   $255.20   $255.20  
  Purchase #3 $58.71   13.758%   $66.7873   $66.79   $66.80   $66.80  
  Purchase #4 $14.79   8.439%   $16.0381   $16.04   $16.05   $16.00  
  Purchase #5 $141.33   7.315%   $151.6683   $151.67   $151.65   $151.70  
  Purchase #6 $191.29   12.466%   $215.1362   $215.14   $215.15   $215.10  
  Purchase #7 $173.73   5.429%   $183.1618   $183.16   $183.15   $183.20  
  7 purchase totals = $1,009.98       $1,113.1632   $1,113.17   $1,113.20   $1,113.20