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	$207.65	4.434%	$216.8572	$216.86	$216.85	$216.90
Purchase #2	$18.48	10.231%	$20.3707	$20.37	$20.35	$20.40
Purchase #3	$10.32	11.330%	$11.4893	$11.49	$11.50	$11.50
Purchase #4	$243.99	12.680%	$274.9279	$274.93	$274.95	$274.90
Purchase #5	$11.92	12.342%	$13.3912	$13.39	$13.40	$13.40
Purchase #6	$104.32	11.460%	$116.2751	$116.28	$116.30	$116.30
Purchase #7	$143.69	13.112%	$162.5306	$162.53	$162.55	$162.50
7 purchase totals =	$740.37		$815.8420	$815.85	$815.90	$815.90