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	$233.83	3.250%	$241.4295	$241.43	$241.45	$241.40
Purchase #2	$100.42	11.145%	$111.6118	$111.61	$111.60	$111.60
Purchase #3	$19.36	6.460%	$20.6107	$20.61	$20.60	$20.60
Purchase #4	$249.31	6.541%	$265.6174	$265.62	$265.60	$265.60
Purchase #5	$71.41	5.555%	$75.3768	$75.38	$75.40	$75.40
Purchase #6	$54.27	3.159%	$55.9844	$55.98	$56.00	$56.00
Purchase #7	$177.91	8.500%	$193.0324	$193.03	$193.05	$193.00
7 purchase totals =	$906.51		$963.6630	$963.66	$963.70	$963.60