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	$36.44	6.853%	$38.9372	$38.94	$38.95	$38.90
Purchase #2	$151.45	4.297%	$157.9578	$157.96	$157.95	$158.00
Purchase #3	$105.88	11.611%	$118.1737	$118.17	$118.15	$118.20
Purchase #4	$173.58	9.753%	$190.5093	$190.51	$190.50	$190.50
Purchase #5	$193.84	11.550%	$216.2285	$216.23	$216.25	$216.20
Purchase #6	$141.78	3.414%	$146.6204	$146.62	$146.60	$146.60
Purchase #7	$164.60	10.532%	$181.9357	$181.94	$181.95	$181.90
7 purchase totals =	$967.57		$1,050.3626	$1,050.37	$1,050.35	$1,050.30