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	$176.61	3.868%	$183.4413	$183.44	$183.45	$183.40
Purchase #2	$207.82	7.211%	$222.8059	$222.81	$222.80	$222.80
Purchase #3	$143.71	8.597%	$156.0647	$156.06	$156.05	$156.10
Purchase #4	$25.64	3.170%	$26.4528	$26.45	$26.45	$26.50
Purchase #5	$69.54	13.289%	$78.7812	$78.78	$78.80	$78.80
Purchase #6	$174.92	12.453%	$196.7028	$196.70	$196.70	$196.70
Purchase #7	$180.92	12.305%	$203.1822	$203.18	$203.20	$203.20
7 purchase totals =	$979.16		$1,067.4309	$1,067.42	$1,067.45	$1,067.50