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	$228.89	9.184%	$249.9113	$249.91	$249.90	$249.90
Purchase #2	$84.88	10.839%	$94.0801	$94.08	$94.10	$94.10
Purchase #3	$13.47	7.290%	$14.452	$14.45	$14.45	$14.50
Purchase #4	$248.44	8.352%	$269.1897	$269.19	$269.20	$269.20
Purchase #5	$189.51	10.598%	$209.5943	$209.59	$209.60	$209.60
Purchase #6	$153.68	12.516%	$172.9146	$172.91	$172.90	$172.90
Purchase #7	$100.30	8.435%	$108.7603	$108.76	$108.75	$108.80
7 purchase totals =	$1,019.17		$1,118.9023	$1,118.89	$1,118.90	$1,119.00