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	$243.82	8.483%	$264.5033	$264.50	$264.50	$264.50
Purchase #2	$215.68	8.820%	$234.703	$234.70	$234.70	$234.70
Purchase #3	$238.73	6.550%	$254.3668	$254.37	$254.35	$254.40
Purchase #4	$48.96	9.696%	$53.7072	$53.71	$53.70	$53.70
Purchase #5	$50.51	4.681%	$52.8744	$52.87	$52.85	$52.90
Purchase #6	$88.60	7.286%	$95.0554	$95.06	$95.05	$95.10
Purchase #7	$212.61	13.638%	$241.6058	$241.61	$241.60	$241.60
7 purchase totals =	$1,098.91		$1,196.8159	$1,196.82	$1,196.75	$1,196.90