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	$77.61	12.450%	$87.2724	$87.27	$87.25	$87.30
Purchase #2	$238.81	6.590%	$254.5476	$254.55	$254.55	$254.50
Purchase #3	$36.91	5.472%	$38.9297	$38.93	$38.95	$38.90
Purchase #4	$238.77	4.781%	$250.1856	$250.19	$250.20	$250.20
Purchase #5	$105.65	11.698%	$118.0089	$118.01	$118.00	$118.00
Purchase #6	$134.27	5.434%	$141.5662	$141.57	$141.55	$141.60
Purchase #7	$214.48	3.233%	$221.4141	$221.41	$221.40	$221.40
7 purchase totals =	$1,046.50		$1,111.9245	$1,111.93	$1,111.90	$1,111.90