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	$238.38	10.459%	$263.3122	$263.31	$263.30	$263.30
Purchase #2	$220.64	12.390%	$247.9773	$247.98	$248.00	$248.00
Purchase #3	$59.56	9.308%	$65.1038	$65.10	$65.10	$65.10
Purchase #4	$147.52	3.776%	$153.0904	$153.09	$153.10	$153.10
Purchase #5	$16.51	13.438%	$18.7286	$18.73	$18.75	$18.70
Purchase #6	$131.51	7.510%	$141.3864	$141.39	$141.40	$141.40
Purchase #7	$156.65	12.145%	$175.6751	$175.68	$175.70	$175.70
7 purchase totals =	$970.77		$1,065.2738	$1,065.28	$1,065.35	$1,065.30