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	$187.55	6.666%	$200.0521	$200.05	$200.05	$200.10
Purchase #2	$247.51	8.838%	$269.3849	$269.38	$269.40	$269.40
Purchase #3	$184.67	4.224%	$192.4705	$192.47	$192.45	$192.50
Purchase #4	$179.61	7.261%	$192.6515	$192.65	$192.65	$192.70
Purchase #5	$35.83	5.771%	$37.8977	$37.90	$37.90	$37.90
Purchase #6	$116.60	12.406%	$131.0654	$131.07	$131.05	$131.10
Purchase #7	$10.25	4.785%	$10.7405	$10.74	$10.75	$10.70
7 purchase totals =	$962.02		$1,034.2626	$1,034.26	$1,034.25	$1,034.40