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	$127.91	8.852%	$139.2326	$139.23	$139.25	$139.20
Purchase #2	$96.32	4.311%	$100.4724	$100.47	$100.45	$100.50
Purchase #3	$205.60	7.801%	$221.6389	$221.64	$221.65	$221.60
Purchase #4	$176.45	11.172%	$196.163	$196.16	$196.15	$196.20
Purchase #5	$232.78	13.773%	$264.8408	$264.84	$264.85	$264.80
Purchase #6	$156.68	9.163%	$171.0366	$171.04	$171.05	$171.00
Purchase #7	$185.25	12.709%	$208.7934	$208.79	$208.80	$208.80
7 purchase totals =	$1,180.99		$1,302.1777	$1,302.17	$1,302.20	$1,302.10