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	$100.86	13.313%	$114.2875	$114.29	$114.30	$114.30
Purchase #2	$102.72	5.391%	$108.2576	$108.26	$108.25	$108.30
Purchase #3	$65.73	10.583%	$72.6862	$72.69	$72.70	$72.70
Purchase #4	$49.83	9.464%	$54.5459	$54.55	$54.55	$54.50
Purchase #5	$38.43	13.800%	$43.7333	$43.73	$43.75	$43.70
Purchase #6	$162.83	6.674%	$173.6973	$173.70	$173.70	$173.70
Purchase #7	$164.39	5.268%	$173.0501	$173.05	$173.05	$173.10
7 purchase totals =	$684.79		$740.2579	$740.27	$740.30	$740.30