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	$57.60	3.788%	$59.7819	$59.78	$59.80	$59.80
Purchase #2	$188.40	4.715%	$197.2831	$197.28	$197.30	$197.30
Purchase #3	$226.50	10.717%	$250.774	$250.77	$250.75	$250.80
Purchase #4	$198.82	12.682%	$224.0344	$224.03	$224.05	$224.00
Purchase #5	$37.69	5.469%	$39.7513	$39.75	$39.75	$39.80
Purchase #6	$170.92	13.549%	$194.078	$194.08	$194.10	$194.10
Purchase #7	$94.54	11.536%	$105.4461	$105.45	$105.45	$105.40
7 purchase totals =	$974.47		$1,071.1488	$1,071.14	$1,071.20	$1,071.20