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	$55.81	9.614%	$61.1756	$61.18	$61.20	$61.20
Purchase #2	$99.94	12.472%	$112.4045	$112.40	$112.40	$112.40
Purchase #3	$20.27	11.600%	$22.6213	$22.62	$22.60	$22.60
Purchase #4	$157.65	11.710%	$176.1108	$176.11	$176.10	$176.10
Purchase #5	$196.62	13.675%	$223.5078	$223.51	$223.50	$223.50
Purchase #6	$139.73	10.275%	$154.0873	$154.09	$154.10	$154.10
Purchase #7	$34.89	10.742%	$38.6379	$38.64	$38.65	$38.60
7 purchase totals =	$704.91		$788.5452	$788.55	$788.55	$788.50