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	$54.89	10.460%	$60.6315	$60.63	$60.65	$60.60
Purchase #2	$109.46	7.815%	$118.0143	$118.01	$118.00	$118.00
Purchase #3	$33.48	12.404%	$37.6329	$37.63	$37.65	$37.60
Purchase #4	$157.84	4.779%	$165.3832	$165.38	$165.40	$165.40
Purchase #5	$49.39	9.616%	$54.1393	$54.14	$54.15	$54.10
Purchase #6	$45.71	8.170%	$49.4445	$49.44	$49.45	$49.40
Purchase #7	$53.64	7.181%	$57.4919	$57.49	$57.50	$57.50
7 purchase totals =	$504.41		$542.7376	$542.72	$542.80	$542.60