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	$86.59	5.378%	$91.2468	$91.25	$91.25	$91.20
Purchase #2	$214.56	4.197%	$223.5651	$223.57	$223.55	$223.60
Purchase #3	$145.57	10.321%	$160.5943	$160.59	$160.60	$160.60
Purchase #4	$46.72	10.436%	$51.5957	$51.60	$51.60	$51.60
Purchase #5	$222.78	5.382%	$234.77	$234.77	$234.75	$234.80
Purchase #6	$239.83	13.628%	$272.514	$272.51	$272.50	$272.50
Purchase #7	$49.83	7.783%	$53.7083	$53.71	$53.70	$53.70
7 purchase totals =	$1,005.88		$1,087.9942	$1,088.00	$1,087.95	$1,088.00