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	$183.98	13.617%	$209.0326	$209.03	$209.05	$209.00
Purchase #2	$100.52	10.641%	$111.2163	$111.22	$111.20	$111.20
Purchase #3	$54.54	6.116%	$57.8757	$57.88	$57.90	$57.90
Purchase #4	$154.48	13.682%	$175.616	$175.62	$175.60	$175.60
Purchase #5	$189.94	4.230%	$197.9745	$197.97	$197.95	$198.00
Purchase #6	$74.65	5.559%	$78.7998	$78.80	$78.80	$78.80
Purchase #7	$81.52	12.665%	$91.8445	$91.84	$91.85	$91.80
7 purchase totals =	$839.63		$922.3594	$922.36	$922.35	$922.30