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 $60.34   4.126%   $62.8296   $62.83   $62.85   $62.80  
  Purchase #2 $136.49   8.618%   $148.2527   $148.25   $148.25   $148.30  
  Purchase #3 $120.72   6.421%   $128.4714   $128.47   $128.45   $128.50  
  Purchase #4 $157.84   6.361%   $167.8802   $167.88   $167.90   $167.90  
  Purchase #5 $47.73   9.182%   $52.1126   $52.11   $52.10   $52.10  
  Purchase #6 $247.71   4.574%   $259.0403   $259.04   $259.05   $259.00  
  Purchase #7 $242.59   3.566%   $251.2408   $251.24   $251.25   $251.20  
  7 purchase totals = $1,013.42       $1,069.8276   $1,069.82   $1,069.85   $1,069.80