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	$55.45	13.237%	$62.7899	$62.79	$62.80	$62.80
Purchase #2	$217.69	4.654%	$227.8213	$227.82	$227.80	$227.80
Purchase #3	$120.38	9.596%	$131.9317	$131.93	$131.95	$131.90
Purchase #4	$194.41	12.680%	$219.0612	$219.06	$219.05	$219.10
Purchase #5	$78.66	5.843%	$83.2561	$83.26	$83.25	$83.30
Purchase #6	$138.59	4.822%	$145.2728	$145.27	$145.25	$145.30
Purchase #7	$250.95	9.388%	$274.5092	$274.51	$274.50	$274.50
7 purchase totals =	$1,056.13		$1,144.6422	$1,144.64	$1,144.60	$1,144.70