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	$68.37	3.104%	$70.4922	$70.49	$70.50	$70.50
Purchase #2	$89.78	6.784%	$95.8707	$95.87	$95.85	$95.90
Purchase #3	$45.86	5.871%	$48.5524	$48.55	$48.55	$48.60
Purchase #4	$33.48	13.850%	$38.117	$38.12	$38.10	$38.10
Purchase #5	$136.96	4.227%	$142.7493	$142.75	$142.75	$142.70
Purchase #6	$238.76	12.865%	$269.4765	$269.48	$269.50	$269.50
Purchase #7	$184.65	10.156%	$203.4031	$203.40	$203.40	$203.40
7 purchase totals =	$797.86		$868.6612	$868.66	$868.65	$868.70