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	$78.39	5.201%	$82.4671	$82.47	$82.45	$82.50
Purchase #2	$48.65	12.448%	$54.706	$54.71	$54.70	$54.70
Purchase #3	$219.25	11.267%	$243.9529	$243.95	$243.95	$244.00
Purchase #4	$69.70	11.559%	$77.7566	$77.76	$77.75	$77.80
Purchase #5	$91.67	9.355%	$100.2457	$100.25	$100.25	$100.20
Purchase #6	$199.60	11.446%	$222.4462	$222.45	$222.45	$222.40
Purchase #7	$103.31	4.602%	$108.0643	$108.06	$108.05	$108.10
7 purchase totals =	$810.57		$889.6388	$889.65	$889.60	$889.70