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	$99.59	13.295%	$112.8305	$112.83	$112.85	$112.80
Purchase #2	$146.52	11.161%	$162.8731	$162.87	$162.85	$162.90
Purchase #3	$20.64	11.713%	$23.0576	$23.06	$23.05	$23.10
Purchase #4	$241.46	5.547%	$254.8538	$254.85	$254.85	$254.90
Purchase #5	$196.65	11.448%	$219.1625	$219.16	$219.15	$219.20
Purchase #6	$226.80	6.506%	$241.5556	$241.56	$241.55	$241.60
Purchase #7	$39.65	4.769%	$41.5409	$41.54	$41.55	$41.50
7 purchase totals =	$971.31		$1,055.8740	$1,055.87	$1,055.85	$1,056.00