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	$160.52	4.419%	$167.6134	$167.61	$167.60	$167.60
Purchase #2	$153.88	8.219%	$166.5274	$166.53	$166.55	$166.50
Purchase #3	$144.29	13.763%	$164.1486	$164.15	$164.15	$164.10
Purchase #4	$238.66	6.851%	$255.0106	$255.01	$255.00	$255.00
Purchase #5	$106.86	12.759%	$120.4943	$120.49	$120.50	$120.50
Purchase #6	$132.51	7.727%	$142.749	$142.75	$142.75	$142.70
Purchase #7	$210.95	4.759%	$220.9891	$220.99	$221.00	$221.00
7 purchase totals =	$1,147.67		$1,237.5324	$1,237.53	$1,237.55	$1,237.40