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	$98.40	4.570%	$102.8969	$102.90	$102.90	$102.90
Purchase #2	$21.32	4.510%	$22.2815	$22.28	$22.30	$22.30
Purchase #3	$147.76	5.461%	$155.8292	$155.83	$155.85	$155.80
Purchase #4	$214.98	7.849%	$231.8538	$231.85	$231.85	$231.90
Purchase #5	$74.58	5.792%	$78.8997	$78.90	$78.90	$78.90
Purchase #6	$109.69	13.704%	$124.7219	$124.72	$124.70	$124.70
Purchase #7	$179.98	10.356%	$198.6187	$198.62	$198.60	$198.60
7 purchase totals =	$846.71		$915.1017	$915.10	$915.10	$915.10