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	$160.64	7.438%	$172.5884	$172.59	$172.60	$172.60
Purchase #2	$152.73	9.110%	$166.6437	$166.64	$166.65	$166.60
Purchase #3	$58.82	3.472%	$60.8622	$60.86	$60.85	$60.90
Purchase #4	$124.57	10.652%	$137.8392	$137.84	$137.85	$137.80
Purchase #5	$95.94	10.360%	$105.8794	$105.88	$105.90	$105.90
Purchase #6	$130.50	5.609%	$137.8197	$137.82	$137.80	$137.80
Purchase #7	$237.49	7.589%	$255.5131	$255.51	$255.50	$255.50
7 purchase totals =	$960.69		$1,037.1457	$1,037.14	$1,037.15	$1,037.10