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	$217.90	11.245%	$242.4029	$242.40	$242.40	$242.40
Purchase #2	$233.76	9.246%	$255.3734	$255.37	$255.35	$255.40
Purchase #3	$134.93	12.444%	$151.7207	$151.72	$151.70	$151.70
Purchase #4	$186.83	13.233%	$211.5532	$211.55	$211.55	$211.60
Purchase #5	$44.38	3.384%	$45.8818	$45.88	$45.90	$45.90
Purchase #6	$129.89	3.586%	$134.5479	$134.55	$134.55	$134.50
Purchase #7	$112.38	10.853%	$124.5766	$124.58	$124.60	$124.60
7 purchase totals =	$1,060.07		$1,166.0565	$1,166.05	$1,166.05	$1,166.10