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	$226.66	7.721%	$244.1604	$244.16	$244.15	$244.20
Purchase #2	$145.43	3.558%	$150.6044	$150.60	$150.60	$150.60
Purchase #3	$99.67	12.260%	$111.8895	$111.89	$111.90	$111.90
Purchase #4	$158.60	6.664%	$169.1691	$169.17	$169.15	$169.20
Purchase #5	$43.54	7.205%	$46.6771	$46.68	$46.70	$46.70
Purchase #6	$207.57	12.227%	$232.9496	$232.95	$232.95	$232.90
Purchase #7	$112.91	13.309%	$127.9372	$127.94	$127.95	$127.90
7 purchase totals =	$994.38		$1,083.3873	$1,083.39	$1,083.40	$1,083.40