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	$57.86	5.439%	$61.007	$61.01	$61.00	$61.00
Purchase #2	$146.49	4.354%	$152.8682	$152.87	$152.85	$152.90
Purchase #3	$49.64	7.222%	$53.225	$53.23	$53.25	$53.20
Purchase #4	$38.85	3.658%	$40.2711	$40.27	$40.25	$40.30
Purchase #5	$18.31	12.169%	$20.5381	$20.54	$20.55	$20.50
Purchase #6	$184.90	11.387%	$205.9546	$205.95	$205.95	$206.00
Purchase #7	$67.82	7.313%	$72.7797	$72.78	$72.80	$72.80
7 purchase totals =	$563.87		$606.6437	$606.65	$606.65	$606.70