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	$103.55	9.540%	$113.4287	$113.43	$113.45	$113.40
Purchase #2	$37.63	10.846%	$41.7113	$41.71	$41.70	$41.70
Purchase #3	$165.40	4.262%	$172.4493	$172.45	$172.45	$172.40
Purchase #4	$69.98	3.623%	$72.5154	$72.52	$72.50	$72.50
Purchase #5	$138.78	8.630%	$150.7567	$150.76	$150.75	$150.80
Purchase #6	$88.81	12.297%	$99.731	$99.73	$99.75	$99.70
Purchase #7	$205.55	13.478%	$233.254	$233.25	$233.25	$233.30
7 purchase totals =	$809.70		$883.8464	$883.85	$883.85	$883.80