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	$150.86	11.254%	$167.8378	$167.84	$167.85	$167.80
Purchase #2	$21.54	9.692%	$23.6277	$23.63	$23.65	$23.60
Purchase #3	$37.83	12.439%	$42.5357	$42.54	$42.55	$42.50
Purchase #4	$74.66	6.162%	$79.2605	$79.26	$79.25	$79.30
Purchase #5	$189.57	3.822%	$196.8154	$196.82	$196.80	$196.80
Purchase #6	$105.95	10.408%	$116.9773	$116.98	$117.00	$117.00
Purchase #7	$125.98	9.253%	$137.6369	$137.64	$137.65	$137.60
7 purchase totals =	$706.39		$764.6913	$764.71	$764.75	$764.60