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	$183.34	4.455%	$191.5078	$191.51	$191.50	$191.50
Purchase #2	$89.39	9.329%	$97.7292	$97.73	$97.75	$97.70
Purchase #3	$157.62	11.868%	$176.3263	$176.33	$176.35	$176.30
Purchase #4	$222.59	5.457%	$234.7367	$234.74	$234.75	$234.70
Purchase #5	$220.34	13.490%	$250.0639	$250.06	$250.05	$250.10
Purchase #6	$87.52	9.323%	$95.6795	$95.68	$95.70	$95.70
Purchase #7	$142.41	5.768%	$150.6242	$150.62	$150.60	$150.60
7 purchase totals =	$1,103.21		$1,196.6676	$1,196.67	$1,196.70	$1,196.60