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	$15.43	7.635%	$16.6081	$16.61	$16.60	$16.60
Purchase #2	$166.56	11.558%	$185.811	$185.81	$185.80	$185.80
Purchase #3	$223.71	4.406%	$233.5667	$233.57	$233.55	$233.60
Purchase #4	$241.96	11.268%	$269.2241	$269.22	$269.20	$269.20
Purchase #5	$63.57	9.494%	$69.6053	$69.61	$69.60	$69.60
Purchase #6	$56.59	4.425%	$59.0941	$59.09	$59.10	$59.10
Purchase #7	$115.57	10.301%	$127.4749	$127.47	$127.45	$127.50
7 purchase totals =	$883.39		$961.3842	$961.38	$961.30	$961.40