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	$115.52	9.430%	$126.4135	$126.41	$126.40	$126.40
Purchase #2	$133.93	9.724%	$146.9534	$146.95	$146.95	$147.00
Purchase #3	$20.38	10.439%	$22.5075	$22.51	$22.50	$22.50
Purchase #4	$234.27	5.783%	$247.8178	$247.82	$247.80	$247.80
Purchase #5	$131.38	13.825%	$149.5433	$149.54	$149.55	$149.50
Purchase #6	$42.44	5.471%	$44.7619	$44.76	$44.75	$44.80
Purchase #7	$100.39	10.851%	$111.2833	$111.28	$111.30	$111.30
7 purchase totals =	$778.31		$849.2807	$849.27	$849.25	$849.30