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	$64.26	12.561%	$72.3317	$72.33	$72.35	$72.30
Purchase #2	$49.37	10.333%	$54.4714	$54.47	$54.45	$54.50
Purchase #3	$191.67	12.824%	$216.2498	$216.25	$216.25	$216.20
Purchase #4	$51.61	5.235%	$54.3118	$54.31	$54.30	$54.30
Purchase #5	$51.29	4.512%	$53.6042	$53.60	$53.60	$53.60
Purchase #6	$241.37	9.233%	$263.6557	$263.66	$263.65	$263.70
Purchase #7	$39.53	7.869%	$42.6406	$42.64	$42.65	$42.60
7 purchase totals =	$689.10		$757.2652	$757.26	$757.25	$757.20