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	$155.76	6.485%	$165.861	$165.86	$165.85	$165.90
Purchase #2	$134.58	13.372%	$152.576	$152.58	$152.60	$152.60
Purchase #3	$23.37	11.669%	$26.097	$26.10	$26.10	$26.10
Purchase #4	$122.75	6.299%	$130.482	$130.48	$130.50	$130.50
Purchase #5	$101.81	9.253%	$111.2305	$111.23	$111.25	$111.20
Purchase #6	$40.60	4.416%	$42.3929	$42.39	$42.40	$42.40
Purchase #7	$74.95	7.395%	$80.4926	$80.49	$80.50	$80.50
7 purchase totals =	$653.82		$709.1320	$709.13	$709.20	$709.20