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	$103.29	8.567%	$112.1389	$112.14	$112.15	$112.10
Purchase #2	$56.27	12.874%	$63.5142	$63.51	$63.50	$63.50
Purchase #3	$63.88	13.147%	$72.2783	$72.28	$72.30	$72.30
Purchase #4	$118.39	4.411%	$123.6122	$123.61	$123.60	$123.60
Purchase #5	$194.57	9.163%	$212.3984	$212.40	$212.40	$212.40
Purchase #6	$10.85	12.810%	$12.2399	$12.24	$12.25	$12.20
Purchase #7	$174.51	4.348%	$182.0977	$182.10	$182.10	$182.10
7 purchase totals =	$721.76		$778.2796	$778.28	$778.30	$778.20