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	$9.51	6.687%	$10.1459	$10.15	$10.15	$10.10
Purchase #2	$237.56	13.373%	$269.3289	$269.33	$269.35	$269.30
Purchase #3	$144.42	11.397%	$160.8795	$160.88	$160.90	$160.90
Purchase #4	$213.43	6.140%	$226.5346	$226.53	$226.55	$226.50
Purchase #5	$146.35	13.518%	$166.1336	$166.13	$166.15	$166.10
Purchase #6	$143.89	3.713%	$149.2326	$149.23	$149.25	$149.20
Purchase #7	$79.85	11.611%	$89.1214	$89.12	$89.10	$89.10
7 purchase totals =	$975.01		$1,071.3765	$1,071.37	$1,071.45	$1,071.20