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	$27.83	5.748%	$29.4297	$29.43	$29.45	$29.40
Purchase #2	$175.60	5.283%	$184.8769	$184.88	$184.90	$184.90
Purchase #3	$215.51	13.580%	$244.7763	$244.78	$244.80	$244.80
Purchase #4	$118.95	6.788%	$127.0243	$127.02	$127.00	$127.00
Purchase #5	$148.56	6.576%	$158.3293	$158.33	$158.35	$158.30
Purchase #6	$74.60	11.794%	$83.3983	$83.40	$83.40	$83.40
Purchase #7	$199.33	13.674%	$226.5864	$226.59	$226.60	$226.60
7 purchase totals =	$960.38		$1,054.4212	$1,054.43	$1,054.50	$1,054.40