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	$241.93	7.573%	$260.2514	$260.25	$260.25	$260.30
Purchase #2	$88.55	11.469%	$98.7058	$98.71	$98.70	$98.70
Purchase #3	$40.99	7.480%	$44.0561	$44.06	$44.05	$44.10
Purchase #4	$187.32	3.528%	$193.9286	$193.93	$193.95	$193.90
Purchase #5	$220.55	6.684%	$235.2916	$235.29	$235.30	$235.30
Purchase #6	$115.77	10.414%	$127.8263	$127.83	$127.85	$127.80
Purchase #7	$56.52	5.686%	$59.7337	$59.73	$59.75	$59.70
7 purchase totals =	$951.63		$1,019.7935	$1,019.80	$1,019.85	$1,019.80