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	$164.91	9.487%	$180.555	$180.56	$180.55	$180.60
Purchase #2	$49.89	9.287%	$54.5233	$54.52	$54.50	$54.50
Purchase #3	$99.43	11.870%	$111.2323	$111.23	$111.25	$111.20
Purchase #4	$10.77	4.334%	$11.2368	$11.24	$11.25	$11.20
Purchase #5	$220.82	3.418%	$228.3676	$228.37	$228.35	$228.40
Purchase #6	$35.92	8.647%	$39.026	$39.03	$39.05	$39.00
Purchase #7	$195.44	13.857%	$222.5221	$222.52	$222.50	$222.50
7 purchase totals =	$777.18		$847.4631	$847.47	$847.45	$847.40