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	$174.80	5.563%	$184.5241	$184.52	$184.50	$184.50
Purchase #2	$216.25	13.255%	$244.9139	$244.91	$244.90	$244.90
Purchase #3	$176.78	10.436%	$195.2288	$195.23	$195.25	$195.20
Purchase #4	$87.27	10.611%	$96.5302	$96.53	$96.55	$96.50
Purchase #5	$49.86	11.683%	$55.6851	$55.69	$55.70	$55.70
Purchase #6	$250.82	8.575%	$272.3278	$272.33	$272.35	$272.30
Purchase #7	$118.25	7.598%	$127.2346	$127.23	$127.25	$127.20
7 purchase totals =	$1,074.03		$1,176.4445	$1,176.44	$1,176.50	$1,176.30