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	$113.85	11.223%	$126.6274	$126.63	$126.65	$126.60
Purchase #2	$245.63	13.563%	$278.9448	$278.94	$278.95	$278.90
Purchase #3	$102.70	8.196%	$111.1173	$111.12	$111.10	$111.10
Purchase #4	$167.30	8.483%	$181.4921	$181.49	$181.50	$181.50
Purchase #5	$212.69	9.790%	$233.5124	$233.51	$233.50	$233.50
Purchase #6	$145.79	5.548%	$153.8784	$153.88	$153.90	$153.90
Purchase #7	$40.48	11.694%	$45.2137	$45.21	$45.20	$45.20
7 purchase totals =	$1,028.44		$1,130.7861	$1,130.78	$1,130.80	$1,130.70