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	$7.68	12.234%	$8.6196	$8.62	$8.60	$8.60
Purchase #2	$78.61	8.608%	$85.3767	$85.38	$85.40	$85.40
Purchase #3	$85.40	5.311%	$89.9356	$89.94	$89.95	$89.90
Purchase #4	$228.94	5.262%	$240.9868	$240.99	$241.00	$241.00
Purchase #5	$129.67	11.315%	$144.3422	$144.34	$144.35	$144.30
Purchase #6	$243.79	7.813%	$262.8373	$262.84	$262.85	$262.80
Purchase #7	$221.59	5.294%	$233.321	$233.32	$233.30	$233.30
7 purchase totals =	$995.68		$1,065.4192	$1,065.43	$1,065.45	$1,065.30