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 $215.48   6.584%   $229.6672   $229.67   $229.65   $229.70  
  Purchase #2 $163.32   4.262%   $170.2807   $170.28   $170.30   $170.30  
  Purchase #3 $67.61   12.597%   $76.1268   $76.13   $76.15   $76.10  
  Purchase #4 $229.50   8.514%   $249.0396   $249.04   $249.05   $249.00  
  Purchase #5 $59.85   11.237%   $66.5753   $66.58   $66.60   $66.60  
  Purchase #6 $152.89   6.580%   $162.9502   $162.95   $162.95   $163.00  
  Purchase #7 $167.33   8.463%   $181.4911   $181.49   $181.50   $181.50  
  7 purchase totals = $1,055.98       $1,136.1309   $1,136.14   $1,136.20   $1,136.20