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	$171.47	13.174%	$194.0595	$194.06	$194.05	$194.10
Purchase #2	$66.42	7.794%	$71.5968	$71.60	$71.60	$71.60
Purchase #3	$138.53	10.184%	$152.6379	$152.64	$152.65	$152.60
Purchase #4	$107.71	5.668%	$113.815	$113.82	$113.80	$113.80
Purchase #5	$100.94	4.340%	$105.3208	$105.32	$105.30	$105.30
Purchase #6	$69.26	11.518%	$77.2374	$77.24	$77.25	$77.20
Purchase #7	$240.75	9.791%	$264.3218	$264.32	$264.30	$264.30
7 purchase totals =	$895.08		$978.9892	$979.00	$978.95	$978.90