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	$52.51	13.610%	$59.6566	$59.66	$59.65	$59.70
Purchase #2	$160.83	7.407%	$172.7427	$172.74	$172.75	$172.70
Purchase #3	$185.92	3.601%	$192.615	$192.62	$192.60	$192.60
Purchase #4	$138.35	12.575%	$155.7475	$155.75	$155.75	$155.70
Purchase #5	$78.27	10.809%	$86.7302	$86.73	$86.75	$86.70
Purchase #6	$45.45	12.551%	$51.1544	$51.15	$51.15	$51.20
Purchase #7	$98.87	6.192%	$104.992	$104.99	$105.00	$105.00
7 purchase totals =	$760.20		$823.6384	$823.64	$823.65	$823.60