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	$57.27	13.203%	$64.8314	$64.83	$64.85	$64.80
Purchase #2	$208.52	6.631%	$222.347	$222.35	$222.35	$222.30
Purchase #3	$95.47	4.150%	$99.432	$99.43	$99.45	$99.40
Purchase #4	$198.77	6.851%	$212.3877	$212.39	$212.40	$212.40
Purchase #5	$64.46	3.455%	$66.6871	$66.69	$66.70	$66.70
Purchase #6	$189.92	11.845%	$212.416	$212.42	$212.40	$212.40
Purchase #7	$202.44	9.171%	$221.0058	$221.01	$221.00	$221.00
7 purchase totals =	$1,016.85		$1,099.1070	$1,099.12	$1,099.15	$1,099.00