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	$235.46	10.124%	$259.298	$259.30	$259.30	$259.30
Purchase #2	$17.52	7.333%	$18.8047	$18.80	$18.80	$18.80
Purchase #3	$145.59	4.270%	$151.8067	$151.81	$151.80	$151.80
Purchase #4	$30.25	12.613%	$34.0654	$34.07	$34.05	$34.10
Purchase #5	$230.61	5.181%	$242.5579	$242.56	$242.55	$242.60
Purchase #6	$211.42	13.627%	$240.2302	$240.23	$240.25	$240.20
Purchase #7	$131.83	13.271%	$149.3252	$149.33	$149.35	$149.30
7 purchase totals =	$1,002.68		$1,096.0881	$1,096.10	$1,096.10	$1,096.10