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	$190.78	6.857%	$203.8618	$203.86	$203.85	$203.90
Purchase #2	$220.66	6.729%	$235.5082	$235.51	$235.50	$235.50
Purchase #3	$41.45	9.428%	$45.3579	$45.36	$45.35	$45.40
Purchase #4	$66.85	7.235%	$71.6866	$71.69	$71.70	$71.70
Purchase #5	$63.87	4.398%	$66.679	$66.68	$66.70	$66.70
Purchase #6	$93.32	13.169%	$105.6093	$105.61	$105.60	$105.60
Purchase #7	$185.32	5.828%	$196.1204	$196.12	$196.10	$196.10
7 purchase totals =	$862.25		$924.8232	$924.83	$924.80	$924.90