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	$82.69	8.749%	$89.9245	$89.92	$89.90	$89.90
Purchase #2	$205.66	4.303%	$214.5095	$214.51	$214.50	$214.50
Purchase #3	$233.59	3.412%	$241.5601	$241.56	$241.55	$241.60
Purchase #4	$232.30	10.313%	$256.2571	$256.26	$256.25	$256.30
Purchase #5	$70.85	6.162%	$75.2158	$75.22	$75.20	$75.20
Purchase #6	$153.30	3.382%	$158.4846	$158.48	$158.50	$158.50
Purchase #7	$52.76	11.122%	$58.628	$58.63	$58.65	$58.60
7 purchase totals =	$1,031.15		$1,094.5796	$1,094.58	$1,094.55	$1,094.60