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 $182.62   8.257%   $197.6989   $197.70   $197.70   $197.70  
  Purchase #2 $121.30   9.677%   $133.0382   $133.04   $133.05   $133.00  
  Purchase #3 $108.64   3.517%   $112.4609   $112.46   $112.45   $112.50  
  Purchase #4 $173.47   7.167%   $185.9026   $185.90   $185.90   $185.90  
  Purchase #5 $200.98   7.634%   $216.3228   $216.32   $216.30   $216.30  
  Purchase #6 $106.64   8.373%   $115.569   $115.57   $115.55   $115.60  
  Purchase #7 $65.68   13.752%   $74.7123   $74.71   $74.70   $74.70  
  7 purchase totals = $959.33       $1,035.7047   $1,035.70   $1,035.65   $1,035.70