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	$114.52	13.438%	$129.9092	$129.91	$129.90	$129.90
Purchase #2	$136.94	12.321%	$153.8124	$153.81	$153.80	$153.80
Purchase #3	$68.56	13.514%	$77.8252	$77.83	$77.85	$77.80
Purchase #4	$164.58	5.656%	$173.8886	$173.89	$173.90	$173.90
Purchase #5	$213.85	9.131%	$233.3766	$233.38	$233.40	$233.40
Purchase #6	$200.55	11.168%	$222.9474	$222.95	$222.95	$222.90
Purchase #7	$70.49	9.260%	$77.0174	$77.02	$77.00	$77.00
7 purchase totals =	$969.49		$1,068.7768	$1,068.79	$1,068.80	$1,068.70