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	$83.30	6.467%	$88.687	$88.69	$88.70	$88.70
Purchase #2	$95.95	5.145%	$100.8866	$100.89	$100.90	$100.90
Purchase #3	$90.83	10.764%	$100.6069	$100.61	$100.60	$100.60
Purchase #4	$216.57	10.123%	$238.4934	$238.49	$238.50	$238.50
Purchase #5	$124.88	4.803%	$130.878	$130.88	$130.90	$130.90
Purchase #6	$126.84	12.444%	$142.624	$142.62	$142.60	$142.60
Purchase #7	$57.89	9.625%	$63.4619	$63.46	$63.45	$63.50
7 purchase totals =	$796.26		$865.6378	$865.64	$865.65	$865.70