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	$99.68	10.776%	$110.4215	$110.42	$110.40	$110.40
Purchase #2	$22.73	3.354%	$23.4924	$23.49	$23.50	$23.50
Purchase #3	$116.38	12.608%	$131.0532	$131.05	$131.05	$131.10
Purchase #4	$56.71	9.652%	$62.1836	$62.18	$62.20	$62.20
Purchase #5	$82.43	10.420%	$91.0192	$91.02	$91.00	$91.00
Purchase #6	$119.56	10.176%	$131.7264	$131.73	$131.75	$131.70
Purchase #7	$102.78	9.224%	$112.2604	$112.26	$112.25	$112.30
7 purchase totals =	$600.27		$662.1567	$662.15	$662.15	$662.20