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	$108.34	10.235%	$119.4286	$119.43	$119.45	$119.40
Purchase #2	$86.61	6.734%	$92.4423	$92.44	$92.45	$92.40
Purchase #3	$87.79	12.314%	$98.6005	$98.60	$98.60	$98.60
Purchase #4	$108.78	13.178%	$123.115	$123.12	$123.10	$123.10
Purchase #5	$207.25	12.474%	$233.1024	$233.10	$233.10	$233.10
Purchase #6	$241.32	5.205%	$253.8807	$253.88	$253.90	$253.90
Purchase #7	$150.58	7.660%	$162.1144	$162.11	$162.10	$162.10
7 purchase totals =	$990.67		$1,082.6839	$1,082.68	$1,082.70	$1,082.60