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	$187.45	4.708%	$196.2751	$196.28	$196.30	$196.30
Purchase #2	$160.37	12.475%	$180.3762	$180.38	$180.40	$180.40
Purchase #3	$55.61	3.466%	$57.5374	$57.54	$57.55	$57.50
Purchase #4	$136.81	4.693%	$143.2305	$143.23	$143.25	$143.20
Purchase #5	$97.86	13.663%	$111.2306	$111.23	$111.25	$111.20
Purchase #6	$20.88	8.151%	$22.5819	$22.58	$22.60	$22.60
Purchase #7	$128.36	12.781%	$144.7657	$144.77	$144.75	$144.80
7 purchase totals =	$787.34		$855.9974	$856.01	$856.10	$856.00