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 $88.77   7.253%   $95.2085   $95.21   $95.20   $95.20  
  Purchase #2 $42.72   10.586%   $47.2423   $47.24   $47.25   $47.20  
  Purchase #3 $242.98   4.405%   $253.6833   $253.68   $253.70   $253.70  
  Purchase #4 $199.95   8.178%   $216.3019   $216.30   $216.30   $216.30  
  Purchase #5 $22.62   7.421%   $24.2986   $24.30   $24.30   $24.30  
  Purchase #6 $117.73   7.334%   $126.3643   $126.36   $126.35   $126.40  
  Purchase #7 $178.93   13.236%   $202.6132   $202.61   $202.60   $202.60  
  7 purchase totals = $893.70       $965.7121   $965.70   $965.70   $965.70