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	$144.58	10.506%	$159.7696	$159.77	$159.75	$159.80
Purchase #2	$231.53	4.629%	$242.2475	$242.25	$242.25	$242.20
Purchase #3	$131.28	4.542%	$137.2427	$137.24	$137.25	$137.20
Purchase #4	$150.31	6.854%	$160.6122	$160.61	$160.60	$160.60
Purchase #5	$122.90	12.338%	$138.0634	$138.06	$138.05	$138.10
Purchase #6	$131.86	10.394%	$145.5655	$145.57	$145.55	$145.60
Purchase #7	$132.36	5.409%	$139.5194	$139.52	$139.50	$139.50
7 purchase totals =	$1,044.82		$1,123.0203	$1,123.02	$1,122.95	$1,123.00