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	$66.82	11.678%	$74.6232	$74.62	$74.60	$74.60
Purchase #2	$103.85	6.254%	$110.3448	$110.34	$110.35	$110.30
Purchase #3	$162.54	5.871%	$172.0827	$172.08	$172.10	$172.10
Purchase #4	$83.93	3.486%	$86.8558	$86.86	$86.85	$86.90
Purchase #5	$244.61	4.623%	$255.9183	$255.92	$255.90	$255.90
Purchase #6	$130.26	5.108%	$136.9137	$136.91	$136.90	$136.90
Purchase #7	$52.39	12.240%	$58.8025	$58.80	$58.80	$58.80
7 purchase totals =	$844.40		$895.5410	$895.53	$895.50	$895.50