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	$233.59	9.731%	$256.3206	$256.32	$256.30	$256.30
Purchase #2	$67.86	6.316%	$72.146	$72.15	$72.15	$72.10
Purchase #3	$222.61	9.390%	$243.5131	$243.51	$243.50	$243.50
Purchase #4	$64.48	4.776%	$67.5596	$67.56	$67.55	$67.60
Purchase #5	$192.59	13.461%	$218.5145	$218.51	$218.50	$218.50
Purchase #6	$250.30	12.707%	$282.1056	$282.11	$282.10	$282.10
Purchase #7	$236.60	6.832%	$252.7645	$252.76	$252.75	$252.80
7 purchase totals =	$1,268.03		$1,392.9239	$1,392.92	$1,392.85	$1,392.90