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	$109.84	12.727%	$123.8193	$123.82	$123.80	$123.80
Purchase #2	$227.31	13.738%	$258.5378	$258.54	$258.55	$258.50
Purchase #3	$90.54	6.158%	$96.1155	$96.12	$96.10	$96.10
Purchase #4	$200.74	13.488%	$227.8158	$227.82	$227.80	$227.80
Purchase #5	$52.43	6.830%	$56.011	$56.01	$56.00	$56.00
Purchase #6	$170.51	6.663%	$181.8711	$181.87	$181.85	$181.90
Purchase #7	$107.77	9.561%	$118.0739	$118.07	$118.05	$118.10
7 purchase totals =	$959.14		$1,062.2444	$1,062.25	$1,062.15	$1,062.20