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	$112.70	6.178%	$119.6626	$119.66	$119.65	$119.70
Purchase #2	$38.72	10.382%	$42.7399	$42.74	$42.75	$42.70
Purchase #3	$53.94	11.725%	$60.2645	$60.26	$60.25	$60.30
Purchase #4	$178.72	6.405%	$190.167	$190.17	$190.15	$190.20
Purchase #5	$177.86	4.211%	$185.3497	$185.35	$185.35	$185.30
Purchase #6	$220.62	4.772%	$231.148	$231.15	$231.15	$231.10
Purchase #7	$12.40	4.204%	$12.9213	$12.92	$12.90	$12.90
7 purchase totals =	$794.96		$842.2530	$842.25	$842.20	$842.20