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	$69.79	9.480%	$76.4061	$76.41	$76.40	$76.40
Purchase #2	$14.54	7.371%	$15.6117	$15.61	$15.60	$15.60
Purchase #3	$160.57	5.152%	$168.8426	$168.84	$168.85	$168.80
Purchase #4	$80.33	11.719%	$89.7439	$89.74	$89.75	$89.70
Purchase #5	$162.61	6.229%	$172.739	$172.74	$172.75	$172.70
Purchase #6	$108.76	13.492%	$123.4339	$123.43	$123.45	$123.40
Purchase #7	$61.44	8.817%	$66.8572	$66.86	$66.85	$66.90
7 purchase totals =	$658.04		$713.6344	$713.63	$713.65	$713.50