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	$148.48	3.121%	$153.1141	$153.11	$153.10	$153.10
Purchase #2	$22.31	13.280%	$25.2728	$25.27	$25.25	$25.30
Purchase #3	$11.31	8.756%	$12.3003	$12.30	$12.30	$12.30
Purchase #4	$131.73	13.133%	$149.0301	$149.03	$149.05	$149.00
Purchase #5	$71.85	9.200%	$78.4602	$78.46	$78.45	$78.50
Purchase #6	$95.67	10.209%	$105.437	$105.44	$105.45	$105.40
Purchase #7	$116.77	5.404%	$123.0803	$123.08	$123.10	$123.10
7 purchase totals =	$598.12		$646.6948	$646.69	$646.70	$646.70