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 $92.81   3.714%   $96.257   $96.26   $96.25   $96.30  
  Purchase #2 $153.44   8.667%   $166.7386   $166.74   $166.75   $166.70  
  Purchase #3 $56.90   3.269%   $58.7601   $58.76   $58.75   $58.80  
  Purchase #4 $227.70   10.323%   $251.2055   $251.21   $251.20   $251.20  
  Purchase #5 $182.80   10.441%   $201.8861   $201.89   $201.90   $201.90  
  Purchase #6 $231.72   7.673%   $249.4999   $249.50   $249.50   $249.50  
  Purchase #7 $155.94   7.703%   $167.9521   $167.95   $167.95   $168.00  
  7 purchase totals = $1,101.31       $1,192.2993   $1,192.31   $1,192.30   $1,192.40