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	$22.65	13.344%	$25.6724	$25.67	$25.65	$25.70
Purchase #2	$80.25	3.284%	$82.8854	$82.89	$82.90	$82.90
Purchase #3	$238.43	6.602%	$254.1711	$254.17	$254.15	$254.20
Purchase #4	$17.52	4.229%	$18.2609	$18.26	$18.25	$18.30
Purchase #5	$74.30	9.802%	$81.5829	$81.58	$81.60	$81.60
Purchase #6	$129.89	12.453%	$146.0652	$146.07	$146.05	$146.10
Purchase #7	$234.45	9.445%	$256.5938	$256.59	$256.60	$256.60
7 purchase totals =	$797.49		$865.2317	$865.23	$865.20	$865.40