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	$105.29	4.274%	$109.7901	$109.79	$109.80	$109.80
Purchase #2	$99.59	9.752%	$109.302	$109.30	$109.30	$109.30
Purchase #3	$204.54	10.808%	$226.6467	$226.65	$226.65	$226.60
Purchase #4	$74.55	11.456%	$83.0904	$83.09	$83.10	$83.10
Purchase #5	$241.92	13.749%	$275.1816	$275.18	$275.20	$275.20
Purchase #6	$222.89	3.332%	$230.3167	$230.32	$230.30	$230.30
Purchase #7	$52.41	13.120%	$59.2862	$59.29	$59.30	$59.30
7 purchase totals =	$1,001.19		$1,093.6137	$1,093.62	$1,093.65	$1,093.60