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	$111.81	11.237%	$124.3741	$124.37	$124.35	$124.40
Purchase #2	$167.68	7.738%	$180.6551	$180.66	$180.65	$180.70
Purchase #3	$6.64	12.125%	$7.4451	$7.45	$7.45	$7.40
Purchase #4	$134.75	3.594%	$139.5929	$139.59	$139.60	$139.60
Purchase #5	$43.56	8.813%	$47.3989	$47.40	$47.40	$47.40
Purchase #6	$184.57	10.150%	$203.3039	$203.30	$203.30	$203.30
Purchase #7	$49.27	4.757%	$51.6138	$51.61	$51.60	$51.60
7 purchase totals =	$698.28		$754.3838	$754.38	$754.35	$754.40