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	$82.76	3.170%	$85.3835	$85.38	$85.40	$85.40
Purchase #2	$90.26	13.188%	$102.1635	$102.16	$102.15	$102.20
Purchase #3	$45.68	10.747%	$50.5892	$50.59	$50.60	$50.60
Purchase #4	$240.73	3.325%	$248.7343	$248.73	$248.75	$248.70
Purchase #5	$206.94	9.562%	$226.7276	$226.73	$226.75	$226.70
Purchase #6	$128.30	11.793%	$143.4304	$143.43	$143.45	$143.40
Purchase #7	$240.41	5.679%	$254.0629	$254.06	$254.05	$254.10
7 purchase totals =	$1,035.08		$1,111.0914	$1,111.08	$1,111.15	$1,111.10