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	$179.92	4.251%	$187.5684	$187.57	$187.55	$187.60
Purchase #2	$75.84	4.365%	$79.1504	$79.15	$79.15	$79.20
Purchase #3	$247.83	12.139%	$277.9141	$277.91	$277.90	$277.90
Purchase #4	$87.61	3.382%	$90.573	$90.57	$90.55	$90.60
Purchase #5	$48.26	13.263%	$54.6607	$54.66	$54.65	$54.70
Purchase #6	$100.58	3.856%	$104.4584	$104.46	$104.45	$104.50
Purchase #7	$201.78	5.378%	$212.6317	$212.63	$212.65	$212.60
7 purchase totals =	$941.82		$1,006.9567	$1,006.95	$1,006.90	$1,007.10