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	$63.38	3.243%	$65.4354	$65.44	$65.45	$65.40
Purchase #2	$41.46	13.674%	$47.1292	$47.13	$47.15	$47.10
Purchase #3	$200.69	9.696%	$220.1489	$220.15	$220.15	$220.10
Purchase #4	$20.70	9.233%	$22.6112	$22.61	$22.60	$22.60
Purchase #5	$93.49	6.536%	$99.6005	$99.60	$99.60	$99.60
Purchase #6	$143.47	11.828%	$160.4396	$160.44	$160.45	$160.40
Purchase #7	$31.58	13.618%	$35.8806	$35.88	$35.90	$35.90
7 purchase totals =	$594.77		$651.2454	$651.25	$651.30	$651.10