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 $176.30   11.138%   $195.9363   $195.94   $195.95   $195.90  
  Purchase #2 $50.81   13.371%   $57.6038   $57.60   $57.60   $57.60  
  Purchase #3 $219.80   3.659%   $227.8425   $227.84   $227.85   $227.80  
  Purchase #4 $173.43   8.431%   $188.0519   $188.05   $188.05   $188.10  
  Purchase #5 $85.73   10.349%   $94.6022   $94.60   $94.60   $94.60  
  Purchase #6 $170.63   12.685%   $192.2744   $192.27   $192.25   $192.30  
  Purchase #7 $181.48   7.396%   $194.9023   $194.90   $194.90   $194.90  
  7 purchase totals = $1,058.18       $1,151.2134   $1,151.20   $1,151.20   $1,151.20