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	$200.61	5.785%	$212.2153	$212.22	$212.20	$212.20
Purchase #2	$120.62	5.828%	$127.6497	$127.65	$127.65	$127.60
Purchase #3	$131.48	3.563%	$136.1646	$136.16	$136.15	$136.20
Purchase #4	$83.40	10.685%	$92.3113	$92.31	$92.30	$92.30
Purchase #5	$243.41	13.444%	$276.134	$276.13	$276.15	$276.10
Purchase #6	$82.89	9.142%	$90.4678	$90.47	$90.45	$90.50
Purchase #7	$10.94	4.814%	$11.4667	$11.47	$11.45	$11.50
7 purchase totals =	$873.35		$946.4094	$946.41	$946.35	$946.40