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	$56.42	10.493%	$62.3402	$62.34	$62.35	$62.30
Purchase #2	$96.87	6.619%	$103.2818	$103.28	$103.30	$103.30
Purchase #3	$126.27	4.457%	$131.8979	$131.90	$131.90	$131.90
Purchase #4	$149.66	8.532%	$162.429	$162.43	$162.45	$162.40
Purchase #5	$237.94	10.650%	$263.2806	$263.28	$263.30	$263.30
Purchase #6	$110.41	8.115%	$119.3698	$119.37	$119.35	$119.40
Purchase #7	$50.85	11.325%	$56.6088	$56.61	$56.60	$56.60
7 purchase totals =	$828.42		$899.2081	$899.21	$899.25	$899.20