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	$142.30	3.137%	$146.764	$146.76	$146.75	$146.80
Purchase #2	$6.29	8.152%	$6.8028	$6.80	$6.80	$6.80
Purchase #3	$239.25	8.447%	$259.4594	$259.46	$259.45	$259.50
Purchase #4	$52.51	5.599%	$55.45	$55.45	$55.45	$55.50
Purchase #5	$132.85	7.823%	$143.2429	$143.24	$143.25	$143.20
Purchase #6	$85.28	4.503%	$89.1202	$89.12	$89.10	$89.10
Purchase #7	$154.71	6.513%	$164.7863	$164.79	$164.80	$164.80
7 purchase totals =	$813.19		$865.6256	$865.62	$865.60	$865.70