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	$250.94	5.533%	$264.8245	$264.82	$264.80	$264.80
Purchase #2	$206.28	7.820%	$222.4111	$222.41	$222.40	$222.40
Purchase #3	$11.92	5.596%	$12.587	$12.59	$12.60	$12.60
Purchase #4	$38.74	5.242%	$40.7708	$40.77	$40.75	$40.80
Purchase #5	$146.65	4.119%	$152.6905	$152.69	$152.70	$152.70
Purchase #6	$89.38	9.280%	$97.6745	$97.67	$97.65	$97.70
Purchase #7	$19.59	11.217%	$21.7874	$21.79	$21.80	$21.80
7 purchase totals =	$763.50		$812.7458	$812.74	$812.70	$812.80