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	$56.89	13.600%	$64.627	$64.63	$64.65	$64.60
Purchase #2	$11.89	8.609%	$12.9136	$12.91	$12.90	$12.90
Purchase #3	$64.48	3.856%	$66.9663	$66.97	$66.95	$67.00
Purchase #4	$54.29	13.154%	$61.4313	$61.43	$61.45	$61.40
Purchase #5	$75.43	4.658%	$78.9435	$78.94	$78.95	$78.90
Purchase #6	$192.31	12.277%	$215.9199	$215.92	$215.90	$215.90
Purchase #7	$19.77	11.536%	$22.0507	$22.05	$22.05	$22.10
7 purchase totals =	$475.06		$522.8523	$522.85	$522.85	$522.80