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	$136.45	5.394%	$143.8101	$143.81	$143.80	$143.80
Purchase #2	$85.27	5.753%	$90.1756	$90.18	$90.20	$90.20
Purchase #3	$68.62	4.483%	$71.6962	$71.70	$71.70	$71.70
Purchase #4	$48.66	13.703%	$55.3279	$55.33	$55.35	$55.30
Purchase #5	$95.89	5.266%	$100.9396	$100.94	$100.95	$100.90
Purchase #6	$235.35	4.554%	$246.0678	$246.07	$246.05	$246.10
Purchase #7	$105.93	8.482%	$114.915	$114.92	$114.90	$114.90
7 purchase totals =	$776.17		$822.9322	$822.95	$822.95	$822.90