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 $87.64   7.513%   $94.2244   $94.22   $94.20   $94.20  
  Purchase #2 $80.97   13.134%   $91.6046   $91.60   $91.60   $91.60  
  Purchase #3 $164.70   6.582%   $175.5406   $175.54   $175.55   $175.50  
  Purchase #4 $178.96   7.328%   $192.0742   $192.07   $192.05   $192.10  
  Purchase #5 $228.60   11.712%   $255.3736   $255.37   $255.35   $255.40  
  Purchase #6 $82.75   12.610%   $93.1848   $93.18   $93.20   $93.20  
  Purchase #7 $57.64   4.756%   $60.3814   $60.38   $60.40   $60.40  
  7 purchase totals = $881.26       $962.3836   $962.36   $962.35   $962.40