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	$176.70	13.547%	$200.6375	$200.64	$200.65	$200.60
Purchase #2	$147.46	5.399%	$155.4214	$155.42	$155.40	$155.40
Purchase #3	$223.30	13.704%	$253.901	$253.90	$253.90	$253.90
Purchase #4	$152.38	3.771%	$158.1262	$158.13	$158.15	$158.10
Purchase #5	$50.51	13.832%	$57.4965	$57.50	$57.50	$57.50
Purchase #6	$142.72	11.580%	$159.247	$159.25	$159.25	$159.20
Purchase #7	$11.63	6.445%	$12.3796	$12.38	$12.40	$12.40
7 purchase totals =	$904.70		$997.2092	$997.22	$997.25	$997.10