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	$143.91	6.312%	$152.9936	$152.99	$153.00	$153.00
Purchase #2	$139.60	7.725%	$150.3841	$150.38	$150.40	$150.40
Purchase #3	$30.50	10.586%	$33.7287	$33.73	$33.75	$33.70
Purchase #4	$187.25	6.409%	$199.2509	$199.25	$199.25	$199.30
Purchase #5	$240.76	9.724%	$264.1715	$264.17	$264.15	$264.20
Purchase #6	$115.51	7.288%	$123.9284	$123.93	$123.95	$123.90
Purchase #7	$33.84	13.243%	$38.3214	$38.32	$38.30	$38.30
7 purchase totals =	$891.37		$962.7786	$962.77	$962.80	$962.80