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	$247.29	10.537%	$273.3469	$273.35	$273.35	$273.30
Purchase #2	$136.35	10.804%	$151.0813	$151.08	$151.10	$151.10
Purchase #3	$35.40	6.537%	$37.7141	$37.71	$37.70	$37.70
Purchase #4	$100.63	10.805%	$111.5031	$111.50	$111.50	$111.50
Purchase #5	$169.77	13.509%	$192.7042	$192.70	$192.70	$192.70
Purchase #6	$32.80	5.366%	$34.56	$34.56	$34.55	$34.60
Purchase #7	$150.29	13.472%	$170.5371	$170.54	$170.55	$170.50
7 purchase totals =	$872.53		$971.4467	$971.44	$971.45	$971.40