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 $229.40   7.214%   $245.9489   $245.95   $245.95   $245.90  
  Purchase #2 $96.37   13.443%   $109.325   $109.33   $109.35   $109.30  
  Purchase #3 $92.68   10.586%   $102.4911   $102.49   $102.50   $102.50  
  Purchase #4 $154.99   8.375%   $167.9704   $167.97   $167.95   $168.00  
  Purchase #5 $166.69   8.484%   $180.832   $180.83   $180.85   $180.80  
  Purchase #6 $196.87   12.187%   $220.8625   $220.86   $220.85   $220.90  
  Purchase #7 $51.97   12.536%   $58.485   $58.49   $58.50   $58.50  
  7 purchase totals = $988.97       $1,085.9149   $1,085.92   $1,085.95   $1,085.90