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	$86.68	4.362%	$90.461	$90.46	$90.45	$90.50
Purchase #2	$170.88	10.699%	$189.1625	$189.16	$189.15	$189.20
Purchase #3	$22.42	7.619%	$24.1282	$24.13	$24.15	$24.10
Purchase #4	$200.75	4.839%	$210.4643	$210.46	$210.45	$210.50
Purchase #5	$179.89	4.588%	$188.1434	$188.14	$188.15	$188.10
Purchase #6	$132.76	10.618%	$146.8565	$146.86	$146.85	$146.90
Purchase #7	$200.55	3.263%	$207.0939	$207.09	$207.10	$207.10
7 purchase totals =	$993.93		$1,056.3098	$1,056.30	$1,056.30	$1,056.40