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	$248.70	4.466%	$259.8069	$259.81	$259.80	$259.80
Purchase #2	$195.75	8.523%	$212.4338	$212.43	$212.45	$212.40
Purchase #3	$78.62	8.572%	$85.3593	$85.36	$85.35	$85.40
Purchase #4	$53.27	5.740%	$56.3277	$56.33	$56.35	$56.30
Purchase #5	$156.43	10.556%	$172.9428	$172.94	$172.95	$172.90
Purchase #6	$153.58	3.627%	$159.1503	$159.15	$159.15	$159.20
Purchase #7	$65.56	10.223%	$72.2622	$72.26	$72.25	$72.30
7 purchase totals =	$951.91		$1,018.2830	$1,018.28	$1,018.30	$1,018.30