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	$142.66	12.246%	$160.1301	$160.13	$160.15	$160.10
Purchase #2	$51.60	13.345%	$58.486	$58.49	$58.50	$58.50
Purchase #3	$45.36	7.823%	$48.9085	$48.91	$48.90	$48.90
Purchase #4	$196.70	9.496%	$215.3786	$215.38	$215.40	$215.40
Purchase #5	$83.32	12.834%	$94.0133	$94.01	$94.00	$94.00
Purchase #6	$198.85	8.382%	$215.5176	$215.52	$215.50	$215.50
Purchase #7	$144.42	5.336%	$152.1263	$152.13	$152.15	$152.10
7 purchase totals =	$862.91		$944.5604	$944.57	$944.60	$944.50