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	$212.28	8.589%	$230.5127	$230.51	$230.50	$230.50
Purchase #2	$71.58	12.277%	$80.3679	$80.37	$80.35	$80.40
Purchase #3	$200.33	11.811%	$223.991	$223.99	$224.00	$224.00
Purchase #4	$125.44	12.756%	$141.4411	$141.44	$141.45	$141.40
Purchase #5	$177.88	10.479%	$196.52	$196.52	$196.50	$196.50
Purchase #6	$248.94	5.403%	$262.3902	$262.39	$262.40	$262.40
Purchase #7	$6.52	10.321%	$7.1929	$7.19	$7.20	$7.20
7 purchase totals =	$1,042.97		$1,142.4158	$1,142.41	$1,142.40	$1,142.40