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 $206.75   7.679%   $222.6263   $222.63   $222.65   $222.60  
  Purchase #2 $163.82   9.415%   $179.2437   $179.24   $179.25   $179.20  
  Purchase #3 $123.25   3.350%   $127.3789   $127.38   $127.40   $127.40  
  Purchase #4 $143.85   10.391%   $158.7975   $158.80   $158.80   $158.80  
  Purchase #5 $150.87   5.775%   $159.5827   $159.58   $159.60   $159.60  
  Purchase #6 $84.97   9.532%   $93.0693   $93.07   $93.05   $93.10  
  Purchase #7 $69.94   5.293%   $73.6419   $73.64   $73.65   $73.60  
  7 purchase totals = $943.45       $1,014.3403   $1,014.34   $1,014.40   $1,014.30