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 $59.38   10.682%   $65.723   $65.72   $65.70   $65.70  
  Purchase #2 $33.64   5.460%   $35.4767   $35.48   $35.50   $35.50  
  Purchase #3 $55.40   8.441%   $60.0763   $60.08   $60.10   $60.10  
  Purchase #4 $104.49   8.782%   $113.6663   $113.67   $113.65   $113.70  
  Purchase #5 $195.92   11.420%   $218.2941   $218.29   $218.30   $218.30  
  Purchase #6 $35.77   6.672%   $38.1566   $38.16   $38.15   $38.20  
  Purchase #7 $89.66   6.801%   $95.7578   $95.76   $95.75   $95.80  
  7 purchase totals = $574.26       $627.1508   $627.16   $627.15   $627.30