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	$59.59	9.161%	$65.049	$65.05	$65.05	$65.00
Purchase #2	$57.54	3.365%	$59.4762	$59.48	$59.50	$59.50
Purchase #3	$213.26	6.671%	$227.4866	$227.49	$227.50	$227.50
Purchase #4	$29.50	7.239%	$31.6355	$31.64	$31.65	$31.60
Purchase #5	$187.62	13.416%	$212.7911	$212.79	$212.80	$212.80
Purchase #6	$44.72	6.833%	$47.7757	$47.78	$47.80	$47.80
Purchase #7	$209.83	9.394%	$229.5414	$229.54	$229.55	$229.50
7 purchase totals =	$802.06		$873.7555	$873.77	$873.85	$873.70