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	$151.39	10.210%	$166.8469	$166.85	$166.85	$166.80
Purchase #2	$26.77	3.460%	$27.6962	$27.70	$27.70	$27.70
Purchase #3	$243.34	12.576%	$273.9424	$273.94	$273.95	$273.90
Purchase #4	$148.98	6.345%	$158.4328	$158.43	$158.45	$158.40
Purchase #5	$161.48	11.143%	$179.4737	$179.47	$179.45	$179.50
Purchase #6	$48.76	12.196%	$54.7068	$54.71	$54.70	$54.70
Purchase #7	$193.66	5.407%	$204.1312	$204.13	$204.15	$204.10
7 purchase totals =	$974.38		$1,065.2300	$1,065.23	$1,065.25	$1,065.10