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	$115.53	13.454%	$131.0734	$131.07	$131.05	$131.10
Purchase #2	$111.41	10.610%	$123.2306	$123.23	$123.25	$123.20
Purchase #3	$12.51	5.302%	$13.1733	$13.17	$13.15	$13.20
Purchase #4	$179.34	6.291%	$190.6223	$190.62	$190.60	$190.60
Purchase #5	$75.91	9.719%	$83.2877	$83.29	$83.30	$83.30
Purchase #6	$67.35	13.431%	$76.3958	$76.40	$76.40	$76.40
Purchase #7	$31.96	11.639%	$35.6798	$35.68	$35.70	$35.70
7 purchase totals =	$594.01		$653.4629	$653.46	$653.45	$653.50