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	$140.87	4.558%	$147.2909	$147.29	$147.30	$147.30
Purchase #2	$158.29	4.331%	$165.1455	$165.15	$165.15	$165.10
Purchase #3	$57.78	3.588%	$59.8531	$59.85	$59.85	$59.90
Purchase #4	$126.49	8.552%	$137.3074	$137.31	$137.30	$137.30
Purchase #5	$249.68	3.587%	$258.636	$258.64	$258.65	$258.60
Purchase #6	$102.26	3.537%	$105.8769	$105.88	$105.90	$105.90
Purchase #7	$56.35	5.207%	$59.2841	$59.28	$59.30	$59.30
7 purchase totals =	$891.72		$933.3939	$933.40	$933.45	$933.40