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	$106.60	6.326%	$113.3435	$113.34	$113.35	$113.30
Purchase #2	$11.76	6.493%	$12.5236	$12.52	$12.50	$12.50
Purchase #3	$12.91	5.627%	$13.6364	$13.64	$13.65	$13.60
Purchase #4	$175.50	5.113%	$184.4733	$184.47	$184.45	$184.50
Purchase #5	$40.35	11.564%	$45.0161	$45.02	$45.00	$45.00
Purchase #6	$197.68	10.842%	$219.1125	$219.11	$219.10	$219.10
Purchase #7	$175.60	5.365%	$185.0209	$185.02	$185.00	$185.00
7 purchase totals =	$720.40		$773.1263	$773.12	$773.05	$773.00