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	$213.68	3.639%	$221.4558	$221.46	$221.45	$221.50
Purchase #2	$100.60	11.674%	$112.344	$112.34	$112.35	$112.30
Purchase #3	$174.31	4.137%	$181.5212	$181.52	$181.50	$181.50
Purchase #4	$128.27	6.466%	$136.5639	$136.56	$136.55	$136.60
Purchase #5	$37.82	9.247%	$41.3172	$41.32	$41.30	$41.30
Purchase #6	$46.64	6.873%	$49.8456	$49.85	$49.85	$49.80
Purchase #7	$157.82	11.813%	$176.4633	$176.46	$176.45	$176.50
7 purchase totals =	$859.14		$919.5110	$919.51	$919.45	$919.50