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	$151.63	4.210%	$158.0136	$158.01	$158.00	$158.00
Purchase #2	$63.55	5.534%	$67.0669	$67.07	$67.05	$67.10
Purchase #3	$78.73	13.239%	$89.1531	$89.15	$89.15	$89.20
Purchase #4	$63.47	5.346%	$66.8631	$66.86	$66.85	$66.90
Purchase #5	$71.75	10.839%	$79.527	$79.53	$79.55	$79.50
Purchase #6	$17.63	12.223%	$19.7849	$19.78	$19.80	$19.80
Purchase #7	$250.87	10.755%	$277.8511	$277.85	$277.85	$277.90
7 purchase totals =	$697.63		$758.2597	$758.25	$758.25	$758.40