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	$121.40	4.568%	$126.9456	$126.95	$126.95	$126.90
Purchase #2	$36.90	10.837%	$40.8989	$40.90	$40.90	$40.90
Purchase #3	$205.77	8.795%	$223.8675	$223.87	$223.85	$223.90
Purchase #4	$159.81	7.698%	$172.1122	$172.11	$172.10	$172.10
Purchase #5	$34.64	3.513%	$35.8569	$35.86	$35.85	$35.90
Purchase #6	$77.53	11.254%	$86.2552	$86.26	$86.25	$86.30
Purchase #7	$46.78	5.808%	$49.497	$49.50	$49.50	$49.50
7 purchase totals =	$682.83		$735.4333	$735.45	$735.40	$735.50