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	$111.93	11.720%	$125.0482	$125.05	$125.05	$125.00
Purchase #2	$159.29	12.701%	$179.5214	$179.52	$179.50	$179.50
Purchase #3	$51.57	10.137%	$56.7977	$56.80	$56.80	$56.80
Purchase #4	$130.41	10.797%	$144.4904	$144.49	$144.50	$144.50
Purchase #5	$48.92	10.480%	$54.0468	$54.05	$54.05	$54.00
Purchase #6	$33.34	13.497%	$37.8399	$37.84	$37.85	$37.80
Purchase #7	$49.64	7.867%	$53.5452	$53.55	$53.55	$53.50
7 purchase totals =	$585.10		$651.2896	$651.30	$651.30	$651.10