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	$120.53	5.874%	$127.6099	$127.61	$127.60	$127.60
Purchase #2	$107.51	8.684%	$116.8462	$116.85	$116.85	$116.80
Purchase #3	$37.95	10.408%	$41.8998	$41.90	$41.90	$41.90
Purchase #4	$20.89	10.236%	$23.0283	$23.03	$23.05	$23.00
Purchase #5	$26.38	5.444%	$27.8161	$27.82	$27.80	$27.80
Purchase #6	$146.45	3.267%	$151.2345	$151.23	$151.25	$151.20
Purchase #7	$102.35	10.706%	$113.3076	$113.31	$113.30	$113.30
7 purchase totals =	$562.06		$601.7424	$601.75	$601.75	$601.60