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	$36.25	5.198%	$38.1343	$38.13	$38.15	$38.10
Purchase #2	$67.32	7.543%	$72.3979	$72.40	$72.40	$72.40
Purchase #3	$112.34	10.556%	$124.1986	$124.20	$124.20	$124.20
Purchase #4	$135.77	12.353%	$152.5417	$152.54	$152.55	$152.50
Purchase #5	$221.31	7.278%	$237.4169	$237.42	$237.40	$237.40
Purchase #6	$158.86	8.433%	$172.2567	$172.26	$172.25	$172.30
Purchase #7	$97.52	5.610%	$102.9909	$102.99	$103.00	$103.00
7 purchase totals =	$829.37		$899.9370	$899.94	$899.95	$899.90