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	$54.50	3.496%	$56.4053	$56.41	$56.40	$56.40
Purchase #2	$123.66	11.404%	$137.7622	$137.76	$137.75	$137.80
Purchase #3	$22.97	6.443%	$24.45	$24.45	$24.45	$24.50
Purchase #4	$151.73	10.432%	$167.5585	$167.56	$167.55	$167.60
Purchase #5	$151.45	3.158%	$156.2328	$156.23	$156.25	$156.20
Purchase #6	$58.32	8.154%	$63.0754	$63.08	$63.10	$63.10
Purchase #7	$150.76	4.724%	$157.8819	$157.88	$157.90	$157.90
7 purchase totals =	$713.39		$763.3661	$763.37	$763.40	$763.50