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	$167.26	7.176%	$179.2626	$179.26	$179.25	$179.30
Purchase #2	$152.77	13.289%	$173.0716	$173.07	$173.05	$173.10
Purchase #3	$17.89	6.503%	$19.0534	$19.05	$19.05	$19.10
Purchase #4	$77.49	6.155%	$82.2595	$82.26	$82.25	$82.30
Purchase #5	$137.67	10.233%	$151.7578	$151.76	$151.75	$151.80
Purchase #6	$209.74	5.657%	$221.605	$221.61	$221.60	$221.60
Purchase #7	$237.92	7.338%	$255.3786	$255.38	$255.40	$255.40
7 purchase totals =	$1,000.74		$1,082.3885	$1,082.39	$1,082.35	$1,082.60