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	$113.89	5.166%	$119.7736	$119.77	$119.75	$119.80
Purchase #2	$70.25	11.764%	$78.5142	$78.51	$78.50	$78.50
Purchase #3	$66.78	5.252%	$70.2873	$70.29	$70.30	$70.30
Purchase #4	$139.62	5.579%	$147.4094	$147.41	$147.40	$147.40
Purchase #5	$34.32	9.519%	$37.5869	$37.59	$37.60	$37.60
Purchase #6	$215.42	10.618%	$238.2933	$238.29	$238.30	$238.30
Purchase #7	$23.40	3.148%	$24.1366	$24.14	$24.15	$24.10
7 purchase totals =	$663.68		$716.0013	$716.00	$716.00	$716.00