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	$151.87	5.187%	$159.7475	$159.75	$159.75	$159.70
Purchase #2	$54.90	13.391%	$62.2517	$62.25	$62.25	$62.30
Purchase #3	$150.45	5.443%	$158.639	$158.64	$158.65	$158.60
Purchase #4	$177.27	10.832%	$196.4719	$196.47	$196.45	$196.50
Purchase #5	$192.85	10.345%	$212.8003	$212.80	$212.80	$212.80
Purchase #6	$163.66	5.393%	$172.4862	$172.49	$172.50	$172.50
Purchase #7	$108.76	11.148%	$120.8846	$120.88	$120.90	$120.90
7 purchase totals =	$999.76		$1,083.2812	$1,083.28	$1,083.30	$1,083.30