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	$69.40	6.482%	$73.8985	$73.90	$73.90	$73.90
Purchase #2	$227.41	11.151%	$252.7685	$252.77	$252.75	$252.80
Purchase #3	$127.49	13.507%	$144.7101	$144.71	$144.70	$144.70
Purchase #4	$114.61	8.640%	$124.5123	$124.51	$124.50	$124.50
Purchase #5	$205.73	13.395%	$233.2875	$233.29	$233.30	$233.30
Purchase #6	$113.50	4.339%	$118.4248	$118.42	$118.40	$118.40
Purchase #7	$75.82	3.503%	$78.476	$78.48	$78.50	$78.50
7 purchase totals =	$933.96		$1,026.0777	$1,026.08	$1,026.05	$1,026.10