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	$114.88	7.210%	$123.1628	$123.16	$123.15	$123.20
Purchase #2	$97.88	7.794%	$105.5088	$105.51	$105.50	$105.50
Purchase #3	$93.94	7.190%	$100.6943	$100.69	$100.70	$100.70
Purchase #4	$192.31	9.438%	$210.4602	$210.46	$210.45	$210.50
Purchase #5	$219.97	6.422%	$234.0965	$234.10	$234.10	$234.10
Purchase #6	$84.56	6.766%	$90.2813	$90.28	$90.30	$90.30
Purchase #7	$19.71	10.370%	$21.7539	$21.75	$21.75	$21.80
7 purchase totals =	$823.25		$885.9578	$885.95	$885.95	$886.10