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	$223.38	3.437%	$231.0576	$231.06	$231.05	$231.10
Purchase #2	$61.42	5.156%	$64.5868	$64.59	$64.60	$64.60
Purchase #3	$250.36	11.131%	$278.2276	$278.23	$278.25	$278.20
Purchase #4	$162.67	6.104%	$172.5994	$172.60	$172.60	$172.60
Purchase #5	$14.52	5.572%	$15.3291	$15.33	$15.35	$15.30
Purchase #6	$150.76	9.539%	$165.141	$165.14	$165.15	$165.10
Purchase #7	$93.92	6.606%	$100.1244	$100.12	$100.10	$100.10
7 purchase totals =	$957.03		$1,027.0659	$1,027.07	$1,027.10	$1,027.00