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	$56.89	6.547%	$60.6146	$60.61	$60.60	$60.60
Purchase #2	$32.87	13.339%	$37.2545	$37.25	$37.25	$37.30
Purchase #3	$35.75	4.802%	$37.4667	$37.47	$37.45	$37.50
Purchase #4	$136.83	10.220%	$150.814	$150.81	$150.80	$150.80
Purchase #5	$16.74	13.443%	$18.9904	$18.99	$19.00	$19.00
Purchase #6	$181.37	3.847%	$188.3473	$188.35	$188.35	$188.30
Purchase #7	$84.44	4.417%	$88.1697	$88.17	$88.15	$88.20
7 purchase totals =	$544.89		$581.6572	$581.65	$581.60	$581.70