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	$89.46	6.307%	$95.1022	$95.10	$95.10	$95.10
Purchase #2	$7.78	8.117%	$8.4115	$8.41	$8.40	$8.40
Purchase #3	$127.61	13.508%	$144.8476	$144.85	$144.85	$144.80
Purchase #4	$18.77	3.574%	$19.4408	$19.44	$19.45	$19.40
Purchase #5	$78.27	5.194%	$82.3353	$82.34	$82.35	$82.30
Purchase #6	$90.50	10.350%	$99.8668	$99.87	$99.85	$99.90
Purchase #7	$230.37	10.801%	$255.2523	$255.25	$255.25	$255.30
7 purchase totals =	$642.76		$705.2565	$705.26	$705.25	$705.20