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	$174.76	9.830%	$191.9389	$191.94	$191.95	$191.90
Purchase #2	$19.80	9.680%	$21.7166	$21.72	$21.70	$21.70
Purchase #3	$102.88	8.123%	$111.2369	$111.24	$111.25	$111.20
Purchase #4	$153.97	12.396%	$173.0561	$173.06	$173.05	$173.10
Purchase #5	$29.27	7.460%	$31.4535	$31.45	$31.45	$31.50
Purchase #6	$56.55	7.161%	$60.5995	$60.60	$60.60	$60.60
Purchase #7	$232.43	4.745%	$243.4588	$243.46	$243.45	$243.50
7 purchase totals =	$769.66		$833.4603	$833.47	$833.45	$833.50