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	$108.87	6.678%	$116.1403	$116.14	$116.15	$116.10
Purchase #2	$242.63	7.844%	$261.6619	$261.66	$261.65	$261.70
Purchase #3	$159.34	3.268%	$164.5472	$164.55	$164.55	$164.50
Purchase #4	$30.51	12.463%	$34.3125	$34.31	$34.30	$34.30
Purchase #5	$233.68	3.552%	$241.9803	$241.98	$242.00	$242.00
Purchase #6	$38.44	10.852%	$42.6115	$42.61	$42.60	$42.60
Purchase #7	$248.56	3.119%	$256.3126	$256.31	$256.30	$256.30
7 purchase totals =	$1,062.03		$1,117.5663	$1,117.56	$1,117.55	$1,117.50