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	$89.65	10.155%	$98.754	$98.75	$98.75	$98.80
Purchase #2	$48.58	9.394%	$53.1436	$53.14	$53.15	$53.10
Purchase #3	$154.78	4.811%	$162.2265	$162.23	$162.25	$162.20
Purchase #4	$131.53	6.275%	$139.7835	$139.78	$139.80	$139.80
Purchase #5	$46.81	13.787%	$53.2637	$53.26	$53.25	$53.30
Purchase #6	$154.91	11.649%	$172.9555	$172.96	$172.95	$173.00
Purchase #7	$175.31	4.189%	$182.6537	$182.65	$182.65	$182.70
7 purchase totals =	$801.57		$862.7805	$862.77	$862.80	$862.90