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	$145.28	6.849%	$155.2302	$155.23	$155.25	$155.20
Purchase #2	$52.66	4.462%	$55.0097	$55.01	$55.00	$55.00
Purchase #3	$69.77	3.414%	$72.1519	$72.15	$72.15	$72.20
Purchase #4	$117.47	8.675%	$127.6605	$127.66	$127.65	$127.70
Purchase #5	$77.62	7.274%	$83.2661	$83.27	$83.25	$83.30
Purchase #6	$138.94	3.360%	$143.6084	$143.61	$143.60	$143.60
Purchase #7	$111.54	4.678%	$116.7578	$116.76	$116.75	$116.80
7 purchase totals =	$713.28		$753.6846	$753.69	$753.65	$753.80