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	$113.48	7.316%	$121.7822	$121.78	$121.80	$121.80
Purchase #2	$145.78	4.399%	$152.1929	$152.19	$152.20	$152.20
Purchase #3	$11.95	3.302%	$12.3446	$12.34	$12.35	$12.30
Purchase #4	$152.95	4.762%	$160.2335	$160.23	$160.25	$160.20
Purchase #5	$80.66	12.422%	$90.6796	$90.68	$90.70	$90.70
Purchase #6	$200.27	11.555%	$223.4112	$223.41	$223.40	$223.40
Purchase #7	$48.59	12.621%	$54.7225	$54.72	$54.70	$54.70
7 purchase totals =	$753.68		$815.3665	$815.35	$815.40	$815.30