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	$217.31	6.356%	$231.1222	$231.12	$231.10	$231.10
Purchase #2	$200.76	5.328%	$211.4565	$211.46	$211.45	$211.50
Purchase #3	$201.90	10.210%	$222.514	$222.51	$222.50	$222.50
Purchase #4	$187.51	4.625%	$196.1823	$196.18	$196.20	$196.20
Purchase #5	$238.44	10.138%	$262.613	$262.61	$262.60	$262.60
Purchase #6	$151.36	13.856%	$172.3324	$172.33	$172.35	$172.30
Purchase #7	$217.62	8.378%	$235.8522	$235.85	$235.85	$235.90
7 purchase totals =	$1,414.90		$1,532.0726	$1,532.06	$1,532.05	$1,532.10