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	$122.61	8.158%	$132.6125	$132.61	$132.60	$132.60
Purchase #2	$42.53	6.506%	$45.297	$45.30	$45.30	$45.30
Purchase #3	$41.78	4.421%	$43.6271	$43.63	$43.65	$43.60
Purchase #4	$98.35	13.243%	$111.3745	$111.37	$111.35	$111.40
Purchase #5	$26.96	8.489%	$29.2486	$29.25	$29.25	$29.20
Purchase #6	$219.74	11.128%	$244.1927	$244.19	$244.20	$244.20
Purchase #7	$103.91	12.493%	$116.8915	$116.89	$116.90	$116.90
7 purchase totals =	$655.88		$723.2439	$723.24	$723.25	$723.20