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	$76.68	8.762%	$83.3987	$83.40	$83.40	$83.40
Purchase #2	$78.68	13.727%	$89.4804	$89.48	$89.50	$89.50
Purchase #3	$142.94	5.812%	$151.2477	$151.25	$151.25	$151.20
Purchase #4	$151.87	3.244%	$156.7967	$156.80	$156.80	$156.80
Purchase #5	$94.32	10.469%	$104.1944	$104.19	$104.20	$104.20
Purchase #6	$21.52	4.748%	$22.5418	$22.54	$22.55	$22.50
Purchase #7	$248.82	7.665%	$267.8921	$267.89	$267.90	$267.90
7 purchase totals =	$814.83		$875.5518	$875.55	$875.60	$875.50