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	$72.93	9.709%	$80.0108	$80.01	$80.00	$80.00
Purchase #2	$54.66	13.441%	$62.0069	$62.01	$62.00	$62.00
Purchase #3	$33.31	3.527%	$34.4848	$34.48	$34.50	$34.50
Purchase #4	$37.64	7.498%	$40.4622	$40.46	$40.45	$40.50
Purchase #5	$57.57	7.846%	$62.0869	$62.09	$62.10	$62.10
Purchase #6	$218.91	4.389%	$228.518	$228.52	$228.50	$228.50
Purchase #7	$108.40	8.489%	$117.6021	$117.60	$117.60	$117.60
7 purchase totals =	$583.42		$625.1717	$625.17	$625.15	$625.20