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 $61.48   7.465%   $66.0695   $66.07   $66.05   $66.10  
  Purchase #2 $213.88   11.209%   $237.8538   $237.85   $237.85   $237.90  
  Purchase #3 $159.54   8.544%   $173.1711   $173.17   $173.15   $173.20  
  Purchase #4 $87.89   7.612%   $94.5802   $94.58   $94.60   $94.60  
  Purchase #5 $133.42   11.432%   $148.6726   $148.67   $148.65   $148.70  
  Purchase #6 $199.89   9.464%   $218.8076   $218.81   $218.80   $218.80  
  Purchase #7 $237.73   11.725%   $265.6038   $265.60   $265.60   $265.60  
  7 purchase totals = $1,093.83       $1,204.7586   $1,204.75   $1,204.70   $1,204.90