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	$105.36	6.466%	$112.1726	$112.17	$112.15	$112.20
Purchase #2	$59.56	13.196%	$67.4195	$67.42	$67.40	$67.40
Purchase #3	$192.82	10.400%	$212.8733	$212.87	$212.85	$212.90
Purchase #4	$10.74	5.814%	$11.3644	$11.36	$11.35	$11.40
Purchase #5	$42.58	12.153%	$47.7547	$47.75	$47.75	$47.80
Purchase #6	$51.37	4.790%	$53.8306	$53.83	$53.85	$53.80
Purchase #7	$37.72	12.573%	$42.4625	$42.46	$42.45	$42.50
7 purchase totals =	$500.15		$547.8776	$547.86	$547.80	$548.00