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	$199.76	4.343%	$208.4356	$208.44	$208.45	$208.40
Purchase #2	$86.60	3.613%	$89.7289	$89.73	$89.75	$89.70
Purchase #3	$242.66	5.286%	$255.487	$255.49	$255.50	$255.50
Purchase #4	$244.41	10.470%	$269.9997	$270.00	$270.00	$270.00
Purchase #5	$55.41	7.444%	$59.5347	$59.53	$59.55	$59.50
Purchase #6	$35.95	13.805%	$40.9129	$40.91	$40.90	$40.90
Purchase #7	$21.29	9.554%	$23.324	$23.32	$23.30	$23.30
7 purchase totals =	$886.08		$947.4228	$947.42	$947.45	$947.30