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	$113.59	12.314%	$127.5775	$127.58	$127.60	$127.60
Purchase #2	$248.99	4.397%	$259.9381	$259.94	$259.95	$259.90
Purchase #3	$44.58	12.679%	$50.2323	$50.23	$50.25	$50.20
Purchase #4	$81.89	4.407%	$85.4989	$85.50	$85.50	$85.50
Purchase #5	$61.60	3.515%	$63.7652	$63.77	$63.75	$63.80
Purchase #6	$226.56	5.418%	$238.835	$238.84	$238.85	$238.80
Purchase #7	$110.57	11.487%	$123.2712	$123.27	$123.25	$123.30
7 purchase totals =	$887.78		$949.1182	$949.13	$949.15	$949.10