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	$41.55	7.298%	$44.5823	$44.58	$44.60	$44.60
Purchase #2	$199.32	5.335%	$209.9537	$209.95	$209.95	$210.00
Purchase #3	$59.46	11.793%	$66.4721	$66.47	$66.45	$66.50
Purchase #4	$81.98	10.868%	$90.8896	$90.89	$90.90	$90.90
Purchase #5	$144.84	5.123%	$152.2602	$152.26	$152.25	$152.30
Purchase #6	$154.96	10.861%	$171.7902	$171.79	$171.80	$171.80
Purchase #7	$163.83	12.708%	$184.6495	$184.65	$184.65	$184.60
7 purchase totals =	$845.94		$920.5976	$920.59	$920.60	$920.70