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	$166.75	7.314%	$178.9461	$178.95	$178.95	$178.90
Purchase #2	$233.33	4.571%	$243.9955	$244.00	$244.00	$244.00
Purchase #3	$141.96	7.296%	$152.3174	$152.32	$152.30	$152.30
Purchase #4	$179.28	6.371%	$190.7019	$190.70	$190.70	$190.70
Purchase #5	$118.33	10.323%	$130.5452	$130.55	$130.55	$130.50
Purchase #6	$50.72	3.244%	$52.3654	$52.37	$52.35	$52.40
Purchase #7	$219.67	12.560%	$247.2606	$247.26	$247.25	$247.30
7 purchase totals =	$1,110.04		$1,196.1321	$1,196.15	$1,196.10	$1,196.10