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	$215.40	6.584%	$229.5819	$229.58	$229.60	$229.60
Purchase #2	$76.29	8.173%	$82.5252	$82.53	$82.55	$82.50
Purchase #3	$195.98	13.238%	$221.9238	$221.92	$221.90	$221.90
Purchase #4	$120.49	11.741%	$134.6367	$134.64	$134.65	$134.60
Purchase #5	$222.89	9.236%	$243.4761	$243.48	$243.50	$243.50
Purchase #6	$226.29	7.104%	$242.3656	$242.37	$242.35	$242.40
Purchase #7	$198.49	4.870%	$208.1565	$208.16	$208.15	$208.20
7 purchase totals =	$1,255.83		$1,362.6658	$1,362.68	$1,362.70	$1,362.70