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	$14.74	4.595%	$15.4173	$15.42	$15.40	$15.40
Purchase #2	$190.71	12.773%	$215.0694	$215.07	$215.05	$215.10
Purchase #3	$152.85	10.259%	$168.5309	$168.53	$168.55	$168.50
Purchase #4	$108.92	6.629%	$116.1403	$116.14	$116.15	$116.10
Purchase #5	$244.88	7.506%	$263.2607	$263.26	$263.25	$263.30
Purchase #6	$102.99	11.181%	$114.5053	$114.51	$114.50	$114.50
Purchase #7	$144.41	5.170%	$151.876	$151.88	$151.90	$151.90
7 purchase totals =	$959.50		$1,044.7999	$1,044.81	$1,044.80	$1,044.80