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	$210.52	9.675%	$230.8878	$230.89	$230.90	$230.90
Purchase #2	$153.39	7.519%	$164.9234	$164.92	$164.90	$164.90
Purchase #3	$137.46	3.419%	$142.1598	$142.16	$142.15	$142.20
Purchase #4	$59.88	5.388%	$63.1063	$63.11	$63.10	$63.10
Purchase #5	$240.78	13.263%	$272.7147	$272.71	$272.70	$272.70
Purchase #6	$48.96	11.145%	$54.4166	$54.42	$54.40	$54.40
Purchase #7	$136.41	6.285%	$144.9834	$144.98	$145.00	$145.00
7 purchase totals =	$987.40		$1,073.1920	$1,073.19	$1,073.15	$1,073.20