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	$161.28	3.466%	$166.87	$166.87	$166.85	$166.90
Purchase #2	$106.91	4.108%	$111.3019	$111.30	$111.30	$111.30
Purchase #3	$174.73	5.645%	$184.5935	$184.59	$184.60	$184.60
Purchase #4	$81.71	4.263%	$85.1933	$85.19	$85.20	$85.20
Purchase #5	$125.49	9.741%	$137.714	$137.71	$137.70	$137.70
Purchase #6	$80.98	5.729%	$85.6193	$85.62	$85.60	$85.60
Purchase #7	$101.50	10.158%	$111.8104	$111.81	$111.80	$111.80
7 purchase totals =	$832.60		$883.1024	$883.09	$883.05	$883.10