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	$52.82	13.327%	$59.8593	$59.86	$59.85	$59.90
Purchase #2	$169.50	6.652%	$180.7751	$180.78	$180.80	$180.80
Purchase #3	$15.99	3.243%	$16.5086	$16.51	$16.50	$16.50
Purchase #4	$17.53	8.728%	$19.06	$19.06	$19.05	$19.10
Purchase #5	$31.97	9.822%	$35.1101	$35.11	$35.10	$35.10
Purchase #6	$111.27	10.818%	$123.3072	$123.31	$123.30	$123.30
Purchase #7	$227.93	11.667%	$254.5226	$254.52	$254.50	$254.50
7 purchase totals =	$627.01		$689.1429	$689.15	$689.10	$689.20