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	$76.27	9.152%	$83.2502	$83.25	$83.25	$83.30
Purchase #2	$96.94	9.198%	$105.8565	$105.86	$105.85	$105.90
Purchase #3	$51.45	5.864%	$54.467	$54.47	$54.45	$54.50
Purchase #4	$144.32	3.413%	$149.2456	$149.25	$149.25	$149.20
Purchase #5	$49.71	8.319%	$53.8454	$53.85	$53.85	$53.80
Purchase #6	$190.46	10.637%	$210.7192	$210.72	$210.70	$210.70
Purchase #7	$90.48	10.310%	$99.8085	$99.81	$99.80	$99.80
7 purchase totals =	$699.63		$757.1924	$757.21	$757.15	$757.20