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	$199.31	11.271%	$221.7742	$221.77	$221.75	$221.80
Purchase #2	$116.62	9.680%	$127.9088	$127.91	$127.90	$127.90
Purchase #3	$137.68	5.282%	$144.9523	$144.95	$144.95	$145.00
Purchase #4	$243.52	11.754%	$272.1433	$272.14	$272.15	$272.10
Purchase #5	$215.90	3.484%	$223.422	$223.42	$223.40	$223.40
Purchase #6	$66.83	10.475%	$73.8304	$73.83	$73.85	$73.80
Purchase #7	$85.67	5.645%	$90.5061	$90.51	$90.50	$90.50
7 purchase totals =	$1,065.53		$1,154.5371	$1,154.53	$1,154.50	$1,154.50