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	$233.78	11.279%	$260.148	$260.15	$260.15	$260.10
Purchase #2	$138.29	9.845%	$151.9047	$151.90	$151.90	$151.90
Purchase #3	$108.62	8.187%	$117.5127	$117.51	$117.50	$117.50
Purchase #4	$150.77	4.504%	$157.5607	$157.56	$157.55	$157.60
Purchase #5	$191.61	13.710%	$217.8797	$217.88	$217.90	$217.90
Purchase #6	$122.31	4.360%	$127.6427	$127.64	$127.65	$127.60
Purchase #7	$49.34	9.685%	$54.1186	$54.12	$54.10	$54.10
7 purchase totals =	$994.72		$1,086.7671	$1,086.76	$1,086.75	$1,086.70