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 $88.31   6.255%   $93.8338   $93.83   $93.85   $93.80  
  Purchase #2 $55.61   8.532%   $60.3546   $60.35   $60.35   $60.40  
  Purchase #3 $112.37   4.640%   $117.584   $117.58   $117.60   $117.60  
  Purchase #4 $171.66   5.601%   $181.2747   $181.27   $181.25   $181.30  
  Purchase #5 $199.30   11.231%   $221.6834   $221.68   $221.70   $221.70  
  Purchase #6 $148.61   3.874%   $154.3672   $154.37   $154.35   $154.40  
  Purchase #7 $105.39   7.509%   $113.3037   $113.30   $113.30   $113.30  
  7 purchase totals = $881.25       $942.4014   $942.38   $942.40   $942.50