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	$61.46	7.209%	$65.8907	$65.89	$65.90	$65.90
Purchase #2	$159.69	11.780%	$178.5015	$178.50	$178.50	$178.50
Purchase #3	$9.32	12.565%	$10.4911	$10.49	$10.50	$10.50
Purchase #4	$24.47	10.698%	$27.0878	$27.09	$27.10	$27.10
Purchase #5	$113.89	9.299%	$124.4806	$124.48	$124.50	$124.50
Purchase #6	$57.79	13.498%	$65.5905	$65.59	$65.60	$65.60
Purchase #7	$209.90	13.176%	$237.5564	$237.56	$237.55	$237.60
7 purchase totals =	$636.52		$709.5986	$709.60	$709.65	$709.70