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 $89.31   6.387%   $95.0142   $95.01   $95.00   $95.00  
  Purchase #2 $173.91   5.377%   $183.2611   $183.26   $183.25   $183.30  
  Purchase #3 $162.27   8.441%   $175.9672   $175.97   $175.95   $176.00  
  Purchase #4 $109.90   5.576%   $116.028   $116.03   $116.05   $116.00  
  Purchase #5 $143.58   11.794%   $160.5138   $160.51   $160.50   $160.50  
  Purchase #6 $141.38   10.154%   $155.7357   $155.74   $155.75   $155.70  
  Purchase #7 $61.27   13.288%   $69.4116   $69.41   $69.40   $69.40  
  7 purchase totals = $881.62       $955.9316   $955.93   $955.90   $955.90