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	$54.55	9.203%	$59.5702	$59.57	$59.55	$59.60
Purchase #2	$244.33	13.191%	$276.5596	$276.56	$276.55	$276.60
Purchase #3	$219.35	12.767%	$247.3544	$247.35	$247.35	$247.40
Purchase #4	$152.61	13.670%	$173.4718	$173.47	$173.45	$173.50
Purchase #5	$239.78	8.671%	$260.5713	$260.57	$260.55	$260.60
Purchase #6	$105.69	8.725%	$114.9115	$114.91	$114.90	$114.90
Purchase #7	$215.35	3.150%	$222.1335	$222.13	$222.15	$222.10
7 purchase totals =	$1,231.66		$1,354.5723	$1,354.56	$1,354.50	$1,354.70