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	$41.77	3.565%	$43.2591	$43.26	$43.25	$43.30
Purchase #2	$133.85	12.859%	$151.0618	$151.06	$151.05	$151.10
Purchase #3	$29.66	9.531%	$32.4869	$32.49	$32.50	$32.50
Purchase #4	$119.81	7.531%	$128.8329	$128.83	$128.85	$128.80
Purchase #5	$31.55	12.781%	$35.5824	$35.58	$35.60	$35.60
Purchase #6	$54.44	10.209%	$59.9978	$60.00	$60.00	$60.00
Purchase #7	$225.83	10.334%	$249.1673	$249.17	$249.15	$249.20
7 purchase totals =	$636.91		$700.3882	$700.39	$700.40	$700.50