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	$77.45	5.376%	$81.6137	$81.61	$81.60	$81.60
Purchase #2	$151.56	10.400%	$167.3222	$167.32	$167.30	$167.30
Purchase #3	$184.59	3.166%	$190.4341	$190.43	$190.45	$190.40
Purchase #4	$209.62	3.158%	$216.2398	$216.24	$216.25	$216.20
Purchase #5	$167.78	4.609%	$175.513	$175.51	$175.50	$175.50
Purchase #6	$13.96	5.110%	$14.6734	$14.67	$14.65	$14.70
Purchase #7	$218.99	9.308%	$239.3736	$239.37	$239.35	$239.40
7 purchase totals =	$1,023.95		$1,085.1698	$1,085.15	$1,085.10	$1,085.10