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	$128.72	10.439%	$142.1571	$142.16	$142.15	$142.20
Purchase #2	$214.32	5.153%	$225.3639	$225.36	$225.35	$225.40
Purchase #3	$51.76	6.725%	$55.2409	$55.24	$55.25	$55.20
Purchase #4	$32.74	13.448%	$37.1429	$37.14	$37.15	$37.10
Purchase #5	$146.75	13.140%	$166.033	$166.03	$166.05	$166.00
Purchase #6	$193.82	13.861%	$220.6854	$220.69	$220.70	$220.70
Purchase #7	$207.87	6.689%	$221.7744	$221.77	$221.75	$221.80
7 purchase totals =	$975.98		$1,068.3976	$1,068.39	$1,068.40	$1,068.40