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	$185.69	7.379%	$199.3921	$199.39	$199.40	$199.40
Purchase #2	$81.40	11.118%	$90.4501	$90.45	$90.45	$90.50
Purchase #3	$214.83	3.249%	$221.8098	$221.81	$221.80	$221.80
Purchase #4	$22.26	11.699%	$24.8642	$24.86	$24.85	$24.90
Purchase #5	$94.88	7.394%	$101.8954	$101.90	$101.90	$101.90
Purchase #6	$47.32	11.745%	$52.8777	$52.88	$52.90	$52.90
Purchase #7	$55.74	13.751%	$63.4048	$63.40	$63.40	$63.40
7 purchase totals =	$702.12		$754.6941	$754.69	$754.70	$754.80