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	$169.54	6.530%	$180.611	$180.61	$180.60	$180.60
Purchase #2	$75.89	3.284%	$78.3822	$78.38	$78.40	$78.40
Purchase #3	$51.83	12.749%	$58.4378	$58.44	$58.45	$58.40
Purchase #4	$5.70	5.842%	$6.033	$6.03	$6.05	$6.00
Purchase #5	$46.35	3.540%	$47.9908	$47.99	$48.00	$48.00
Purchase #6	$19.72	8.741%	$21.4437	$21.44	$21.45	$21.40
Purchase #7	$55.47	6.776%	$59.2286	$59.23	$59.25	$59.20
7 purchase totals =	$424.50		$452.1271	$452.12	$452.20	$452.00