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	$111.34	6.239%	$118.2865	$118.29	$118.30	$118.30
Purchase #2	$85.89	4.761%	$89.9792	$89.98	$90.00	$90.00
Purchase #3	$122.70	8.522%	$133.1565	$133.16	$133.15	$133.20
Purchase #4	$131.83	7.424%	$141.6171	$141.62	$141.60	$141.60
Purchase #5	$228.41	7.471%	$245.4745	$245.47	$245.45	$245.50
Purchase #6	$225.78	9.745%	$247.7823	$247.78	$247.80	$247.80
Purchase #7	$86.59	11.707%	$96.7271	$96.73	$96.75	$96.70
7 purchase totals =	$992.54		$1,073.0232	$1,073.03	$1,073.05	$1,073.10