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 $169.68   3.128%   $174.9876   $174.99   $175.00   $175.00  
  Purchase #2 $165.75   11.321%   $184.5146   $184.51   $184.50   $184.50  
  Purchase #3 $86.77   10.790%   $96.1325   $96.13   $96.15   $96.10  
  Purchase #4 $131.62   3.499%   $136.2254   $136.23   $136.25   $136.20  
  Purchase #5 $183.36   6.488%   $195.2564   $195.26   $195.25   $195.30  
  Purchase #6 $86.91   5.633%   $91.8056   $91.81   $91.80   $91.80  
  Purchase #7 $79.76   6.818%   $85.198   $85.20   $85.20   $85.20  
  7 purchase totals = $903.85       $964.1201   $964.13   $964.15   $964.10