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	$98.67	11.504%	$110.021	$110.02	$110.00	$110.00
Purchase #2	$133.96	13.215%	$151.6628	$151.66	$151.65	$151.70
Purchase #3	$133.32	4.371%	$139.1474	$139.15	$139.15	$139.10
Purchase #4	$200.94	5.237%	$211.4632	$211.46	$211.45	$211.50
Purchase #5	$39.70	7.243%	$42.5755	$42.58	$42.60	$42.60
Purchase #6	$91.30	10.526%	$100.9102	$100.91	$100.90	$100.90
Purchase #7	$61.57	7.836%	$66.3946	$66.39	$66.40	$66.40
7 purchase totals =	$759.46		$822.1747	$822.17	$822.15	$822.20