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	$76.68	5.851%	$81.1665	$81.17	$81.15	$81.20
Purchase #2	$113.81	11.714%	$127.1417	$127.14	$127.15	$127.10
Purchase #3	$72.50	10.517%	$80.1248	$80.12	$80.10	$80.10
Purchase #4	$126.91	11.682%	$141.7356	$141.74	$141.75	$141.70
Purchase #5	$64.88	3.647%	$67.2462	$67.25	$67.25	$67.20
Purchase #6	$157.68	13.254%	$178.5789	$178.58	$178.60	$178.60
Purchase #7	$181.81	4.814%	$190.5623	$190.56	$190.55	$190.60
7 purchase totals =	$794.27		$866.5560	$866.56	$866.55	$866.50