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	$190.81	5.310%	$200.942	$200.94	$200.95	$200.90
Purchase #2	$235.71	13.422%	$267.347	$267.35	$267.35	$267.30
Purchase #3	$194.52	5.270%	$204.7712	$204.77	$204.75	$204.80
Purchase #4	$84.59	7.155%	$90.6424	$90.64	$90.65	$90.60
Purchase #5	$84.95	6.632%	$90.5839	$90.58	$90.60	$90.60
Purchase #6	$93.27	4.183%	$97.1715	$97.17	$97.15	$97.20
Purchase #7	$194.58	12.538%	$218.9764	$218.98	$219.00	$219.00
7 purchase totals =	$1,078.43		$1,170.4344	$1,170.43	$1,170.45	$1,170.40