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	$94.62	11.619%	$105.6139	$105.61	$105.60	$105.60
Purchase #2	$174.38	5.505%	$183.9796	$183.98	$184.00	$184.00
Purchase #3	$56.34	9.721%	$61.8168	$61.82	$61.80	$61.80
Purchase #4	$206.90	13.787%	$235.4253	$235.43	$235.45	$235.40
Purchase #5	$17.62	6.247%	$18.7207	$18.72	$18.70	$18.70
Purchase #6	$114.78	13.261%	$130.001	$130.00	$130.00	$130.00
Purchase #7	$37.26	13.838%	$42.416	$42.42	$42.40	$42.40
7 purchase totals =	$701.90		$777.9733	$777.98	$777.95	$777.90