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	$173.60	5.698%	$183.4917	$183.49	$183.50	$183.50
Purchase #2	$189.33	12.818%	$213.5983	$213.60	$213.60	$213.60
Purchase #3	$103.62	7.865%	$111.7697	$111.77	$111.75	$111.80
Purchase #4	$117.44	4.612%	$122.8563	$122.86	$122.85	$122.90
Purchase #5	$153.50	13.311%	$173.9324	$173.93	$173.95	$173.90
Purchase #6	$233.34	11.294%	$259.6934	$259.69	$259.70	$259.70
Purchase #7	$44.25	3.556%	$45.8235	$45.82	$45.80	$45.80
7 purchase totals =	$1,015.08		$1,111.1653	$1,111.16	$1,111.15	$1,111.20