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 $202.81   11.521%   $226.1757   $226.18   $226.20   $226.20  
  Purchase #2 $218.46   10.442%   $241.2716   $241.27   $241.25   $241.30  
  Purchase #3 $148.86   12.652%   $167.6938   $167.69   $167.70   $167.70  
  Purchase #4 $15.62   11.336%   $17.3907   $17.39   $17.40   $17.40  
  Purchase #5 $202.76   5.195%   $213.2934   $213.29   $213.30   $213.30  
  Purchase #6 $48.87   7.348%   $52.461   $52.46   $52.45   $52.50  
  Purchase #7 $136.30   6.532%   $145.2031   $145.20   $145.20   $145.20  
  7 purchase totals = $973.68       $1,063.4893   $1,063.48   $1,063.50   $1,063.60