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	$63.69	6.455%	$67.8012	$67.80	$67.80	$67.80
Purchase #2	$152.31	6.575%	$162.3244	$162.32	$162.30	$162.30
Purchase #3	$72.31	6.276%	$76.8482	$76.85	$76.85	$76.80
Purchase #4	$66.88	4.815%	$70.1003	$70.10	$70.10	$70.10
Purchase #5	$206.50	5.864%	$218.6092	$218.61	$218.60	$218.60
Purchase #6	$41.57	12.143%	$46.6178	$46.62	$46.60	$46.60
Purchase #7	$60.49	11.529%	$67.4639	$67.46	$67.45	$67.50
7 purchase totals =	$663.75		$709.7650	$709.76	$709.70	$709.70