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	$97.53	13.870%	$111.0574	$111.06	$111.05	$111.10
Purchase #2	$121.28	9.428%	$132.7143	$132.71	$132.70	$132.70
Purchase #3	$74.65	11.102%	$82.9376	$82.94	$82.95	$82.90
Purchase #4	$93.90	3.601%	$97.2813	$97.28	$97.30	$97.30
Purchase #5	$153.59	7.683%	$165.3903	$165.39	$165.40	$165.40
Purchase #6	$249.58	6.125%	$264.8668	$264.87	$264.85	$264.90
Purchase #7	$214.60	4.558%	$224.3815	$224.38	$224.40	$224.40
7 purchase totals =	$1,005.13		$1,078.6292	$1,078.63	$1,078.65	$1,078.70