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	$217.86	12.407%	$244.8899	$244.89	$244.90	$244.90
Purchase #2	$73.99	6.585%	$78.8622	$78.86	$78.85	$78.90
Purchase #3	$132.91	3.390%	$137.4156	$137.42	$137.40	$137.40
Purchase #4	$24.95	3.828%	$25.9051	$25.91	$25.90	$25.90
Purchase #5	$189.65	13.566%	$215.3779	$215.38	$215.40	$215.40
Purchase #6	$23.60	7.122%	$25.2808	$25.28	$25.30	$25.30
Purchase #7	$31.63	5.669%	$33.4231	$33.42	$33.40	$33.40
7 purchase totals =	$694.59		$761.1546	$761.16	$761.15	$761.20