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	$109.72	7.131%	$117.5441	$117.54	$117.55	$117.50
Purchase #2	$50.26	6.567%	$53.5606	$53.56	$53.55	$53.60
Purchase #3	$225.64	13.130%	$255.2665	$255.27	$255.25	$255.30
Purchase #4	$38.34	4.480%	$40.0576	$40.06	$40.05	$40.10
Purchase #5	$215.49	10.827%	$238.8211	$238.82	$238.80	$238.80
Purchase #6	$238.45	5.426%	$251.3883	$251.39	$251.40	$251.40
Purchase #7	$73.42	4.494%	$76.7195	$76.72	$76.70	$76.70
7 purchase totals =	$951.32		$1,033.3577	$1,033.36	$1,033.30	$1,033.40