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	$147.28	7.417%	$158.2038	$158.20	$158.20	$158.20
Purchase #2	$98.52	13.219%	$111.5434	$111.54	$111.55	$111.50
Purchase #3	$10.54	7.310%	$11.3105	$11.31	$11.30	$11.30
Purchase #4	$203.46	6.860%	$217.4174	$217.42	$217.40	$217.40
Purchase #5	$10.77	13.720%	$12.2476	$12.25	$12.25	$12.20
Purchase #6	$188.60	11.154%	$209.6364	$209.64	$209.65	$209.60
Purchase #7	$144.53	5.365%	$152.284	$152.28	$152.30	$152.30
7 purchase totals =	$803.70		$872.6431	$872.64	$872.65	$872.50