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	$132.94	7.164%	$142.4638	$142.46	$142.45	$142.50
Purchase #2	$236.59	11.689%	$264.245	$264.25	$264.25	$264.20
Purchase #3	$53.63	13.700%	$60.9773	$60.98	$61.00	$61.00
Purchase #4	$16.50	9.826%	$18.1213	$18.12	$18.10	$18.10
Purchase #5	$120.57	5.599%	$127.3207	$127.32	$127.30	$127.30
Purchase #6	$60.28	4.406%	$62.9359	$62.94	$62.95	$62.90
Purchase #7	$118.75	6.646%	$126.6421	$126.64	$126.65	$126.60
7 purchase totals =	$739.26		$802.7061	$802.71	$802.70	$802.60