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 $200.32   5.469%   $211.2755   $211.28   $211.30   $211.30  
  Purchase #2 $60.64   8.233%   $65.6325   $65.63   $65.65   $65.60  
  Purchase #3 $167.98   13.265%   $190.2625   $190.26   $190.25   $190.30  
  Purchase #4 $167.76   4.259%   $174.9049   $174.90   $174.90   $174.90  
  Purchase #5 $74.64   6.155%   $79.2341   $79.23   $79.25   $79.20  
  Purchase #6 $183.68   5.818%   $194.3665   $194.37   $194.35   $194.40  
  Purchase #7 $22.87   8.218%   $24.7495   $24.75   $24.75   $24.70  
  7 purchase totals = $877.89       $940.4255   $940.42   $940.45   $940.40