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	$62.82	4.764%	$65.8127	$65.81	$65.80	$65.80
Purchase #2	$250.49	7.493%	$269.2592	$269.26	$269.25	$269.30
Purchase #3	$83.54	3.867%	$86.7705	$86.77	$86.75	$86.80
Purchase #4	$132.79	9.753%	$145.741	$145.74	$145.75	$145.70
Purchase #5	$67.62	10.451%	$74.687	$74.69	$74.70	$74.70
Purchase #6	$98.31	5.403%	$103.6217	$103.62	$103.60	$103.60
Purchase #7	$153.64	12.285%	$172.5147	$172.51	$172.50	$172.50
7 purchase totals =	$849.21		$918.4068	$918.40	$918.35	$918.40