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	$233.44	4.649%	$244.2926	$244.29	$244.30	$244.30
Purchase #2	$103.80	7.252%	$111.3276	$111.33	$111.35	$111.30
Purchase #3	$133.40	7.621%	$143.5664	$143.57	$143.55	$143.60
Purchase #4	$166.38	9.702%	$182.5222	$182.52	$182.50	$182.50
Purchase #5	$176.25	8.222%	$190.7413	$190.74	$190.75	$190.70
Purchase #6	$134.79	10.667%	$149.168	$149.17	$149.15	$149.20
Purchase #7	$129.92	11.871%	$145.3428	$145.34	$145.35	$145.30
7 purchase totals =	$1,077.98		$1,166.9609	$1,166.96	$1,166.95	$1,166.90