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	$91.60	13.373%	$103.8497	$103.85	$103.85	$103.80
Purchase #2	$95.63	10.771%	$105.9303	$105.93	$105.95	$105.90
Purchase #3	$118.44	11.873%	$132.5024	$132.50	$132.50	$132.50
Purchase #4	$241.56	9.601%	$264.7522	$264.75	$264.75	$264.80
Purchase #5	$100.75	10.824%	$111.6552	$111.66	$111.65	$111.70
Purchase #6	$166.56	10.233%	$183.6041	$183.60	$183.60	$183.60
Purchase #7	$147.46	10.774%	$163.3473	$163.35	$163.35	$163.30
7 purchase totals =	$962.00		$1,065.6412	$1,065.64	$1,065.65	$1,065.60