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 $62.57   11.304%   $69.6429   $69.64   $69.65   $69.60  
  Purchase #2 $94.36   4.214%   $98.3363   $98.34   $98.35   $98.30  
  Purchase #3 $198.39   8.799%   $215.8463   $215.85   $215.85   $215.80  
  Purchase #4 $172.54   10.706%   $191.0121   $191.01   $191.00   $191.00  
  Purchase #5 $119.25   5.108%   $125.3413   $125.34   $125.35   $125.30  
  Purchase #6 $174.58   13.571%   $198.2723   $198.27   $198.25   $198.30  
  Purchase #7 $237.35   4.664%   $248.42   $248.42   $248.40   $248.40  
  7 purchase totals = $1,059.04       $1,146.8712   $1,146.87   $1,146.85   $1,146.70