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	$35.29	6.250%	$37.4956	$37.50	$37.50	$37.50
Purchase #2	$230.87	10.561%	$255.2522	$255.25	$255.25	$255.30
Purchase #3	$42.43	11.197%	$47.1809	$47.18	$47.20	$47.20
Purchase #4	$234.29	9.552%	$256.6694	$256.67	$256.65	$256.70
Purchase #5	$166.30	4.164%	$173.2247	$173.22	$173.20	$173.20
Purchase #6	$45.64	13.336%	$51.7266	$51.73	$51.75	$51.70
Purchase #7	$130.72	10.742%	$144.7619	$144.76	$144.75	$144.80
7 purchase totals =	$885.54		$966.3113	$966.31	$966.30	$966.40