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	$248.62	3.738%	$257.9134	$257.91	$257.90	$257.90
Purchase #2	$59.35	3.200%	$61.2492	$61.25	$61.25	$61.20
Purchase #3	$123.28	3.453%	$127.5369	$127.54	$127.55	$127.50
Purchase #4	$65.75	10.589%	$72.7123	$72.71	$72.70	$72.70
Purchase #5	$205.88	13.474%	$233.6203	$233.62	$233.60	$233.60
Purchase #6	$127.45	3.680%	$132.1402	$132.14	$132.15	$132.10
Purchase #7	$113.74	8.650%	$123.5785	$123.58	$123.60	$123.60
7 purchase totals =	$944.07		$1,008.7508	$1,008.75	$1,008.75	$1,008.60