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	$221.65	8.668%	$240.8626	$240.86	$240.85	$240.90
Purchase #2	$231.82	4.420%	$242.0664	$242.07	$242.05	$242.10
Purchase #3	$153.27	7.180%	$164.2748	$164.27	$164.25	$164.30
Purchase #4	$210.98	8.354%	$228.6053	$228.61	$228.60	$228.60
Purchase #5	$32.84	7.332%	$35.2478	$35.25	$35.25	$35.20
Purchase #6	$224.51	13.675%	$255.2117	$255.21	$255.20	$255.20
Purchase #7	$95.38	4.375%	$99.5529	$99.55	$99.55	$99.60
7 purchase totals =	$1,170.45		$1,265.8215	$1,265.82	$1,265.75	$1,265.90