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	$229.75	11.786%	$256.8283	$256.83	$256.85	$256.80
Purchase #2	$248.55	10.601%	$274.8988	$274.90	$274.90	$274.90
Purchase #3	$41.36	10.564%	$45.7293	$45.73	$45.75	$45.70
Purchase #4	$17.53	5.665%	$18.5231	$18.52	$18.50	$18.50
Purchase #5	$116.31	9.267%	$127.0884	$127.09	$127.10	$127.10
Purchase #6	$104.87	10.724%	$116.1163	$116.12	$116.10	$116.10
Purchase #7	$195.35	5.588%	$206.2662	$206.27	$206.25	$206.30
7 purchase totals =	$953.72		$1,045.4504	$1,045.46	$1,045.45	$1,045.40