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	$120.68	9.685%	$132.3679	$132.37	$132.35	$132.40
Purchase #2	$59.29	13.187%	$67.1086	$67.11	$67.10	$67.10
Purchase #3	$156.74	10.257%	$172.8168	$172.82	$172.80	$172.80
Purchase #4	$226.47	12.347%	$254.4323	$254.43	$254.45	$254.40
Purchase #5	$194.43	8.598%	$211.1471	$211.15	$211.15	$211.10
Purchase #6	$155.51	13.514%	$176.5256	$176.53	$176.55	$176.50
Purchase #7	$73.64	13.766%	$83.7773	$83.78	$83.80	$83.80
7 purchase totals =	$986.76		$1,098.1756	$1,098.19	$1,098.20	$1,098.10