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	$141.35	7.686%	$152.2142	$152.21	$152.20	$152.20
Purchase #2	$64.50	4.797%	$67.5941	$67.59	$67.60	$67.60
Purchase #3	$147.49	7.303%	$158.2612	$158.26	$158.25	$158.30
Purchase #4	$122.67	6.601%	$130.7674	$130.77	$130.75	$130.80
Purchase #5	$153.50	3.136%	$158.3138	$158.31	$158.30	$158.30
Purchase #6	$113.75	11.823%	$127.1987	$127.20	$127.20	$127.20
Purchase #7	$207.82	7.789%	$224.0071	$224.01	$224.00	$224.00
7 purchase totals =	$951.08		$1,018.3565	$1,018.35	$1,018.30	$1,018.40