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	$73.65	6.597%	$78.5087	$78.51	$78.50	$78.50
Purchase #2	$49.25	4.564%	$51.4978	$51.50	$51.50	$51.50
Purchase #3	$150.62	5.175%	$158.4146	$158.41	$158.40	$158.40
Purchase #4	$76.80	7.802%	$82.7919	$82.79	$82.80	$82.80
Purchase #5	$162.28	8.332%	$175.8012	$175.80	$175.80	$175.80
Purchase #6	$30.28	11.525%	$33.7698	$33.77	$33.75	$33.80
Purchase #7	$192.51	6.300%	$204.6381	$204.64	$204.65	$204.60
7 purchase totals =	$735.39		$785.4221	$785.42	$785.40	$785.40