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	$145.40	4.833%	$152.4272	$152.43	$152.45	$152.40
Purchase #2	$75.35	4.440%	$78.6955	$78.70	$78.70	$78.70
Purchase #3	$88.42	4.310%	$92.2309	$92.23	$92.25	$92.20
Purchase #4	$215.50	6.718%	$229.9773	$229.98	$230.00	$230.00
Purchase #5	$141.54	7.672%	$152.3989	$152.40	$152.40	$152.40
Purchase #6	$116.40	9.313%	$127.2403	$127.24	$127.25	$127.20
Purchase #7	$141.32	4.734%	$148.0101	$148.01	$148.00	$148.00
7 purchase totals =	$923.93		$980.9802	$980.99	$981.05	$980.90