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	$153.52	13.734%	$174.6044	$174.60	$174.60	$174.60
Purchase #2	$92.76	7.374%	$99.6001	$99.60	$99.60	$99.60
Purchase #3	$250.35	11.202%	$278.3942	$278.39	$278.40	$278.40
Purchase #4	$145.51	13.231%	$164.7624	$164.76	$164.75	$164.80
Purchase #5	$158.31	3.433%	$163.7448	$163.74	$163.75	$163.70
Purchase #6	$54.97	11.419%	$61.247	$61.25	$61.25	$61.20
Purchase #7	$79.67	4.374%	$83.1548	$83.15	$83.15	$83.20
7 purchase totals =	$935.09		$1,025.5077	$1,025.49	$1,025.50	$1,025.50