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	$99.81	6.437%	$106.2348	$106.23	$106.25	$106.20
Purchase #2	$191.77	5.553%	$202.419	$202.42	$202.40	$202.40
Purchase #3	$151.67	5.243%	$159.6221	$159.62	$159.60	$159.60
Purchase #4	$96.82	7.296%	$103.884	$103.88	$103.90	$103.90
Purchase #5	$9.41	10.526%	$10.4005	$10.40	$10.40	$10.40
Purchase #6	$151.86	13.742%	$172.7286	$172.73	$172.75	$172.70
Purchase #7	$29.85	4.426%	$31.1712	$31.17	$31.15	$31.20
7 purchase totals =	$731.19		$786.4602	$786.45	$786.45	$786.40