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	$180.69	9.154%	$197.2304	$197.23	$197.25	$197.20
Purchase #2	$217.28	5.572%	$229.3868	$229.39	$229.40	$229.40
Purchase #3	$98.32	13.376%	$111.4713	$111.47	$111.45	$111.50
Purchase #4	$133.60	13.146%	$151.1631	$151.16	$151.15	$151.20
Purchase #5	$53.57	13.794%	$60.9594	$60.96	$60.95	$61.00
Purchase #6	$17.57	3.638%	$18.2092	$18.21	$18.20	$18.20
Purchase #7	$145.57	5.710%	$153.882	$153.88	$153.90	$153.90
7 purchase totals =	$846.60		$922.3022	$922.30	$922.30	$922.40