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	$196.37	10.249%	$216.496	$216.50	$216.50	$216.50
Purchase #2	$172.82	9.704%	$189.5905	$189.59	$189.60	$189.60
Purchase #3	$95.32	10.841%	$105.6536	$105.65	$105.65	$105.70
Purchase #4	$231.50	4.627%	$242.2115	$242.21	$242.20	$242.20
Purchase #5	$9.27	7.688%	$9.9827	$9.98	$10.00	$10.00
Purchase #6	$81.64	9.188%	$89.1411	$89.14	$89.15	$89.10
Purchase #7	$213.90	10.728%	$236.8472	$236.85	$236.85	$236.80
7 purchase totals =	$1,000.82		$1,089.9226	$1,089.92	$1,089.95	$1,089.90