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	$234.40	6.256%	$249.0641	$249.06	$249.05	$249.10
Purchase #2	$223.54	7.870%	$241.1326	$241.13	$241.15	$241.10
Purchase #3	$30.86	3.180%	$31.8413	$31.84	$31.85	$31.80
Purchase #4	$63.45	13.603%	$72.0811	$72.08	$72.10	$72.10
Purchase #5	$89.76	10.763%	$99.4209	$99.42	$99.40	$99.40
Purchase #6	$123.99	6.607%	$132.182	$132.18	$132.20	$132.20
Purchase #7	$240.43	5.695%	$254.1225	$254.12	$254.10	$254.10
7 purchase totals =	$1,006.43		$1,079.8445	$1,079.83	$1,079.85	$1,079.80