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 $69.81   8.411%   $75.6817   $75.68   $75.70   $75.70  
  Purchase #2 $137.62   10.779%   $152.4541   $152.45   $152.45   $152.50  
  Purchase #3 $59.36   13.146%   $67.1635   $67.16   $67.15   $67.20  
  Purchase #4 $103.47   8.268%   $112.0249   $112.02   $112.00   $112.00  
  Purchase #5 $152.82   3.330%   $157.9089   $157.91   $157.90   $157.90  
  Purchase #6 $221.56   5.184%   $233.0457   $233.05   $233.05   $233.00  
  Purchase #7 $92.50   4.578%   $96.7347   $96.73   $96.75   $96.70  
  7 purchase totals = $837.14       $895.0135   $895.00   $895.00   $895.00