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	$52.91	4.187%	$55.1253	$55.13	$55.15	$55.10
Purchase #2	$40.47	12.322%	$45.4567	$45.46	$45.45	$45.50
Purchase #3	$132.83	3.673%	$137.7088	$137.71	$137.70	$137.70
Purchase #4	$132.99	8.514%	$144.3128	$144.31	$144.30	$144.30
Purchase #5	$61.39	13.206%	$69.4972	$69.50	$69.50	$69.50
Purchase #6	$246.70	3.822%	$256.1289	$256.13	$256.15	$256.10
Purchase #7	$165.52	4.358%	$172.7334	$172.73	$172.75	$172.70
7 purchase totals =	$832.81		$880.9631	$880.97	$881.00	$880.90