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	$45.60	8.785%	$49.606	$49.61	$49.60	$49.60
Purchase #2	$63.92	3.741%	$66.3112	$66.31	$66.30	$66.30
Purchase #3	$164.29	3.522%	$170.0763	$170.08	$170.10	$170.10
Purchase #4	$18.87	7.675%	$20.3183	$20.32	$20.30	$20.30
Purchase #5	$245.40	9.725%	$269.2652	$269.27	$269.25	$269.30
Purchase #6	$213.52	13.569%	$242.4925	$242.49	$242.50	$242.50
Purchase #7	$220.29	11.404%	$245.4119	$245.41	$245.40	$245.40
7 purchase totals =	$971.89		$1,063.4814	$1,063.49	$1,063.45	$1,063.50