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	$90.34	3.776%	$93.7512	$93.75	$93.75	$93.80
Purchase #2	$47.51	13.836%	$54.0835	$54.08	$54.10	$54.10
Purchase #3	$104.78	6.341%	$111.4241	$111.42	$111.40	$111.40
Purchase #4	$131.28	9.144%	$143.2842	$143.28	$143.30	$143.30
Purchase #5	$59.25	13.411%	$67.196	$67.20	$67.20	$67.20
Purchase #6	$79.25	13.102%	$89.6333	$89.63	$89.65	$89.60
Purchase #7	$153.83	5.200%	$161.8292	$161.83	$161.85	$161.80
7 purchase totals =	$666.24		$721.2015	$721.19	$721.25	$721.20