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	$102.65	8.172%	$111.0386	$111.04	$111.05	$111.00
Purchase #2	$95.37	10.205%	$105.1025	$105.10	$105.10	$105.10
Purchase #3	$16.97	7.674%	$18.2723	$18.27	$18.25	$18.30
Purchase #4	$170.82	11.170%	$189.9006	$189.90	$189.90	$189.90
Purchase #5	$117.98	4.534%	$123.3292	$123.33	$123.35	$123.30
Purchase #6	$164.36	10.763%	$182.0501	$182.05	$182.05	$182.10
Purchase #7	$233.77	9.204%	$255.2862	$255.29	$255.30	$255.30
7 purchase totals =	$901.92		$984.9795	$984.98	$985.00	$985.00