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	$127.94	13.537%	$145.2592	$145.26	$145.25	$145.30
Purchase #2	$141.84	6.834%	$151.5333	$151.53	$151.55	$151.50
Purchase #3	$208.58	11.275%	$232.0974	$232.10	$232.10	$232.10
Purchase #4	$167.51	6.583%	$178.5372	$178.54	$178.55	$178.50
Purchase #5	$153.49	11.695%	$171.4407	$171.44	$171.45	$171.40
Purchase #6	$83.90	9.809%	$92.1298	$92.13	$92.15	$92.10
Purchase #7	$91.99	8.243%	$99.5727	$99.57	$99.55	$99.60
7 purchase totals =	$975.25		$1,070.5703	$1,070.57	$1,070.60	$1,070.50