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	$170.75	8.481%	$185.2313	$185.23	$185.25	$185.20
Purchase #2	$133.78	7.748%	$144.1453	$144.15	$144.15	$144.10
Purchase #3	$37.83	11.241%	$42.0825	$42.08	$42.10	$42.10
Purchase #4	$53.71	6.587%	$57.2479	$57.25	$57.25	$57.20
Purchase #5	$76.66	7.592%	$82.48	$82.48	$82.50	$82.50
Purchase #6	$214.79	4.578%	$224.6231	$224.62	$224.60	$224.60
Purchase #7	$8.81	5.717%	$9.3137	$9.31	$9.30	$9.30
7 purchase totals =	$696.33		$745.1238	$745.12	$745.15	$745.00