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 $149.84   13.132%   $169.517   $169.52   $169.50   $169.50  
  Purchase #2 $197.51   3.678%   $204.7744   $204.77   $204.75   $204.80  
  Purchase #3 $26.69   13.268%   $30.2312   $30.23   $30.25   $30.20  
  Purchase #4 $230.38   4.594%   $240.9637   $240.96   $240.95   $241.00  
  Purchase #5 $206.88   9.215%   $225.944   $225.94   $225.95   $225.90  
  Purchase #6 $199.83   4.119%   $208.061   $208.06   $208.05   $208.10  
  Purchase #7 $155.62   6.306%   $165.4334   $165.43   $165.45   $165.40  
  7 purchase totals = $1,166.75       $1,244.9247   $1,244.91   $1,244.90   $1,244.90