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	$32.32	5.291%	$34.0301	$34.03	$34.05	$34.00
Purchase #2	$172.49	9.488%	$188.8559	$188.86	$188.85	$188.90
Purchase #3	$29.91	7.532%	$32.1628	$32.16	$32.15	$32.20
Purchase #4	$117.71	11.873%	$131.6857	$131.69	$131.70	$131.70
Purchase #5	$185.57	8.224%	$200.8313	$200.83	$200.85	$200.80
Purchase #6	$130.47	6.194%	$138.5513	$138.55	$138.55	$138.60
Purchase #7	$120.63	4.705%	$126.3056	$126.31	$126.30	$126.30
7 purchase totals =	$789.10		$852.4227	$852.43	$852.45	$852.50