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	$44.95	12.391%	$50.5198	$50.52	$50.50	$50.50
Purchase #2	$24.82	3.149%	$25.6016	$25.60	$25.60	$25.60
Purchase #3	$11.47	11.205%	$12.7552	$12.76	$12.75	$12.80
Purchase #4	$7.72	11.103%	$8.5772	$8.58	$8.60	$8.60
Purchase #5	$70.29	9.222%	$76.7721	$76.77	$76.75	$76.80
Purchase #6	$216.29	4.422%	$225.8543	$225.85	$225.85	$225.90
Purchase #7	$41.69	3.106%	$42.9849	$42.98	$43.00	$43.00
7 purchase totals =	$417.23		$443.0651	$443.06	$443.05	$443.20