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	$59.85	12.176%	$67.1373	$67.14	$67.15	$67.10
Purchase #2	$157.80	10.133%	$173.7899	$173.79	$173.80	$173.80
Purchase #3	$156.27	8.740%	$169.928	$169.93	$169.95	$169.90
Purchase #4	$236.55	9.435%	$258.8685	$258.87	$258.85	$258.90
Purchase #5	$186.50	10.309%	$205.7263	$205.73	$205.75	$205.70
Purchase #6	$13.57	6.112%	$14.3994	$14.40	$14.40	$14.40
Purchase #7	$122.54	6.116%	$130.0345	$130.03	$130.05	$130.00
7 purchase totals =	$933.08		$1,019.8839	$1,019.89	$1,019.95	$1,019.80