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	$54.49	9.468%	$59.6491	$59.65	$59.65	$59.60
Purchase #2	$151.43	6.435%	$161.1745	$161.17	$161.15	$161.20
Purchase #3	$86.59	3.322%	$89.4665	$89.47	$89.45	$89.50
Purchase #4	$40.39	10.395%	$44.5885	$44.59	$44.60	$44.60
Purchase #5	$156.86	7.603%	$168.7861	$168.79	$168.80	$168.80
Purchase #6	$118.91	10.307%	$131.1661	$131.17	$131.15	$131.20
Purchase #7	$43.98	4.608%	$46.0066	$46.01	$46.00	$46.00
7 purchase totals =	$652.65		$700.8374	$700.85	$700.80	$700.90