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	$103.95	5.749%	$109.9261	$109.93	$109.95	$109.90
Purchase #2	$93.78	6.464%	$99.8419	$99.84	$99.85	$99.80
Purchase #3	$212.80	9.534%	$233.0884	$233.09	$233.10	$233.10
Purchase #4	$36.82	12.510%	$41.4262	$41.43	$41.45	$41.40
Purchase #5	$68.84	4.771%	$72.1244	$72.12	$72.10	$72.10
Purchase #6	$87.76	13.341%	$99.4681	$99.47	$99.45	$99.50
Purchase #7	$83.29	8.856%	$90.6662	$90.67	$90.65	$90.70
7 purchase totals =	$687.24		$746.5413	$746.55	$746.55	$746.50