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	$93.79	12.804%	$105.7989	$105.80	$105.80	$105.80
Purchase #2	$95.56	3.621%	$99.0202	$99.02	$99.00	$99.00
Purchase #3	$158.46	12.235%	$177.8476	$177.85	$177.85	$177.80
Purchase #4	$120.59	5.615%	$127.3611	$127.36	$127.35	$127.40
Purchase #5	$54.90	11.288%	$61.0971	$61.10	$61.10	$61.10
Purchase #6	$214.55	9.721%	$235.4064	$235.41	$235.40	$235.40
Purchase #7	$91.81	13.826%	$104.5037	$104.50	$104.50	$104.50
7 purchase totals =	$829.66		$911.0350	$911.04	$911.00	$911.00