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 $195.53   4.670%   $204.6613   $204.66   $204.65   $204.70  
  Purchase #2 $89.38   5.232%   $94.0564   $94.06   $94.05   $94.10  
  Purchase #3 $65.41   6.404%   $69.5989   $69.60   $69.60   $69.60  
  Purchase #4 $207.91   5.209%   $218.74   $218.74   $218.75   $218.70  
  Purchase #5 $102.98   8.316%   $111.5438   $111.54   $111.55   $111.50  
  Purchase #6 $6.93   5.516%   $7.3123   $7.31   $7.30   $7.30  
  Purchase #7 $157.31   8.247%   $170.2834   $170.28   $170.30   $170.30  
  7 purchase totals = $825.45       $876.1961   $876.19   $876.20   $876.20