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	$196.74	8.824%	$214.1003	$214.10	$214.10	$214.10
Purchase #2	$143.56	8.297%	$155.4712	$155.47	$155.45	$155.50
Purchase #3	$88.69	12.165%	$99.4791	$99.48	$99.50	$99.50
Purchase #4	$196.64	13.474%	$223.1353	$223.14	$223.15	$223.10
Purchase #5	$51.86	4.656%	$54.2746	$54.27	$54.25	$54.30
Purchase #6	$108.88	11.838%	$121.7692	$121.77	$121.75	$121.80
Purchase #7	$129.75	7.781%	$139.8458	$139.85	$139.85	$139.80
7 purchase totals =	$916.12		$1,008.0755	$1,008.08	$1,008.05	$1,008.10