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	$104.62	4.634%	$109.4681	$109.47	$109.45	$109.50
Purchase #2	$222.48	3.502%	$230.2712	$230.27	$230.25	$230.30
Purchase #3	$141.54	7.756%	$152.5178	$152.52	$152.50	$152.50
Purchase #4	$48.99	12.757%	$55.2397	$55.24	$55.25	$55.20
Purchase #5	$167.73	12.451%	$188.6141	$188.61	$188.60	$188.60
Purchase #6	$177.59	12.491%	$199.7728	$199.77	$199.75	$199.80
Purchase #7	$236.85	9.505%	$259.3626	$259.36	$259.35	$259.40
7 purchase totals =	$1,099.80		$1,195.2463	$1,195.24	$1,195.15	$1,195.30