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	$208.26	10.672%	$230.4855	$230.49	$230.50	$230.50
Purchase #2	$49.86	6.304%	$53.0032	$53.00	$53.00	$53.00
Purchase #3	$211.30	7.642%	$227.4475	$227.45	$227.45	$227.40
Purchase #4	$171.56	9.807%	$188.3849	$188.38	$188.40	$188.40
Purchase #5	$65.52	3.490%	$67.8066	$67.81	$67.80	$67.80
Purchase #6	$152.51	3.789%	$158.2886	$158.29	$158.30	$158.30
Purchase #7	$143.67	5.697%	$151.8549	$151.85	$151.85	$151.90
7 purchase totals =	$1,002.68		$1,077.2712	$1,077.27	$1,077.30	$1,077.30