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 $98.49   3.162%   $101.6043   $101.60   $101.60   $101.60  
  Purchase #2 $176.68   9.584%   $193.613   $193.61   $193.60   $193.60  
  Purchase #3 $161.54   7.472%   $173.6103   $173.61   $173.60   $173.60  
  Purchase #4 $91.91   5.288%   $96.7702   $96.77   $96.75   $96.80  
  Purchase #5 $206.83   9.242%   $225.9452   $225.95   $225.95   $225.90  
  Purchase #6 $63.64   13.308%   $72.1092   $72.11   $72.10   $72.10  
  Purchase #7 $81.65   7.807%   $88.0244   $88.02   $88.00   $88.00  
  7 purchase totals = $880.74       $951.6766   $951.67   $951.60   $951.60