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	$111.53	13.523%	$126.6122	$126.61	$126.60	$126.60
Purchase #2	$167.71	10.138%	$184.7124	$184.71	$184.70	$184.70
Purchase #3	$181.27	5.636%	$191.4864	$191.49	$191.50	$191.50
Purchase #4	$84.82	6.647%	$90.458	$90.46	$90.45	$90.50
Purchase #5	$20.86	5.302%	$21.966	$21.97	$21.95	$22.00
Purchase #6	$57.56	13.215%	$65.1666	$65.17	$65.15	$65.20
Purchase #7	$229.48	11.252%	$255.3011	$255.30	$255.30	$255.30
7 purchase totals =	$853.23		$935.7027	$935.71	$935.65	$935.80