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	$124.55	4.723%	$130.4325	$130.43	$130.45	$130.40
Purchase #2	$147.94	3.826%	$153.6002	$153.60	$153.60	$153.60
Purchase #3	$149.40	4.782%	$156.5443	$156.54	$156.55	$156.50
Purchase #4	$47.72	13.132%	$53.9866	$53.99	$54.00	$54.00
Purchase #5	$39.27	4.109%	$40.8836	$40.88	$40.90	$40.90
Purchase #6	$213.87	9.388%	$233.9481	$233.95	$233.95	$233.90
Purchase #7	$6.49	7.853%	$6.9997	$7.00	$7.00	$7.00
7 purchase totals =	$729.24		$776.3950	$776.39	$776.45	$776.30