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 $183.59   6.538%   $195.5931   $195.59   $195.60   $195.60  
  Purchase #2 $70.55   3.135%   $72.7617   $72.76   $72.75   $72.80  
  Purchase #3 $57.60   12.527%   $64.8156   $64.82   $64.80   $64.80  
  Purchase #4 $99.67   6.736%   $106.3838   $106.38   $106.40   $106.40  
  Purchase #5 $179.74   4.722%   $188.2273   $188.23   $188.25   $188.20  
  Purchase #6 $146.96   8.702%   $159.7485   $159.75   $159.75   $159.70  
  Purchase #7 $146.78   10.205%   $161.7589   $161.76   $161.75   $161.80  
  7 purchase totals = $884.89       $949.2889   $949.29   $949.30   $949.30