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	$88.72	10.766%	$98.2716	$98.27	$98.25	$98.30
Purchase #2	$185.80	3.114%	$191.5858	$191.59	$191.60	$191.60
Purchase #3	$29.56	12.271%	$33.1873	$33.19	$33.20	$33.20
Purchase #4	$83.48	13.320%	$94.5995	$94.60	$94.60	$94.60
Purchase #5	$177.82	4.801%	$186.3571	$186.36	$186.35	$186.40
Purchase #6	$53.82	11.429%	$59.9711	$59.97	$59.95	$60.00
Purchase #7	$228.71	4.720%	$239.5051	$239.51	$239.50	$239.50
7 purchase totals =	$847.91		$903.4775	$903.49	$903.45	$903.60