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 $53.58   13.330%   $60.7222   $60.72   $60.70   $60.70  
  Purchase #2 $171.25   12.632%   $192.8823   $192.88   $192.90   $192.90  
  Purchase #3 $150.45   12.476%   $169.2201   $169.22   $169.20   $169.20  
  Purchase #4 $76.76   5.311%   $80.8367   $80.84   $80.85   $80.80  
  Purchase #5 $192.65   4.610%   $201.5312   $201.53   $201.55   $201.50  
  Purchase #6 $198.36   8.655%   $215.5281   $215.53   $215.55   $215.50  
  Purchase #7 $238.55   9.812%   $261.9565   $261.96   $261.95   $262.00  
  7 purchase totals = $1,081.60       $1,182.6771   $1,182.68   $1,182.70   $1,182.60