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	$157.54	3.148%	$162.4994	$162.50	$162.50	$162.50
Purchase #2	$120.85	9.464%	$132.2872	$132.29	$132.30	$132.30
Purchase #3	$24.85	5.308%	$26.169	$26.17	$26.15	$26.20
Purchase #4	$217.78	12.522%	$245.0504	$245.05	$245.05	$245.10
Purchase #5	$74.88	4.663%	$78.3717	$78.37	$78.35	$78.40
Purchase #6	$29.90	11.202%	$33.2494	$33.25	$33.25	$33.20
Purchase #7	$37.37	3.118%	$38.5352	$38.54	$38.55	$38.50
7 purchase totals =	$663.17		$716.1623	$716.17	$716.15	$716.20