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	$101.98	4.833%	$106.9087	$106.91	$106.90	$106.90
Purchase #2	$156.50	8.443%	$169.7133	$169.71	$169.70	$169.70
Purchase #3	$114.25	12.749%	$128.8157	$128.82	$128.80	$128.80
Purchase #4	$132.64	11.584%	$148.005	$148.01	$148.00	$148.00
Purchase #5	$205.81	4.578%	$215.232	$215.23	$215.25	$215.20
Purchase #6	$173.40	4.457%	$181.1284	$181.13	$181.15	$181.10
Purchase #7	$100.92	13.327%	$114.3696	$114.37	$114.35	$114.40
7 purchase totals =	$985.50		$1,064.1727	$1,064.18	$1,064.15	$1,064.10