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	$127.52	13.454%	$144.6765	$144.68	$144.70	$144.70
Purchase #2	$62.86	6.237%	$66.7806	$66.78	$66.80	$66.80
Purchase #3	$59.91	4.213%	$62.434	$62.43	$62.45	$62.40
Purchase #4	$190.49	9.783%	$209.1256	$209.13	$209.15	$209.10
Purchase #5	$23.34	6.143%	$24.7738	$24.77	$24.75	$24.80
Purchase #6	$94.44	9.223%	$103.1502	$103.15	$103.15	$103.20
Purchase #7	$105.33	11.173%	$117.0985	$117.10	$117.10	$117.10
7 purchase totals =	$663.89		$728.0392	$728.04	$728.10	$728.10