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	$10.29	11.211%	$11.4436	$11.44	$11.45	$11.40
Purchase #2	$164.76	11.779%	$184.1671	$184.17	$184.15	$184.20
Purchase #3	$58.89	13.863%	$67.0539	$67.05	$67.05	$67.10
Purchase #4	$103.93	4.250%	$108.347	$108.35	$108.35	$108.30
Purchase #5	$203.37	11.410%	$226.5745	$226.57	$226.55	$226.60
Purchase #6	$141.69	11.704%	$158.2734	$158.27	$158.25	$158.30
Purchase #7	$246.89	4.204%	$257.2693	$257.27	$257.25	$257.30
7 purchase totals =	$929.82		$1,013.1288	$1,013.12	$1,013.05	$1,013.20