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 $73.44   4.529%   $76.7661   $76.77   $76.75   $76.80  
  Purchase #2 $245.42   7.133%   $262.9258   $262.93   $262.95   $262.90  
  Purchase #3 $139.72   10.628%   $154.5694   $154.57   $154.55   $154.60  
  Purchase #4 $54.28   12.679%   $61.1622   $61.16   $61.15   $61.20  
  Purchase #5 $92.92   9.282%   $101.5448   $101.54   $101.55   $101.50  
  Purchase #6 $176.27   12.807%   $198.8449   $198.84   $198.85   $198.80  
  Purchase #7 $193.68   7.153%   $207.5339   $207.53   $207.55   $207.50  
  7 purchase totals = $975.73       $1,063.3471   $1,063.34   $1,063.35   $1,063.30