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	$33.40	12.491%	$37.572	$37.57	$37.55	$37.60
Purchase #2	$243.60	5.511%	$257.0248	$257.02	$257.00	$257.00
Purchase #3	$213.51	7.838%	$230.2449	$230.24	$230.25	$230.20
Purchase #4	$52.83	7.780%	$56.9402	$56.94	$56.95	$56.90
Purchase #5	$19.53	8.365%	$21.1637	$21.16	$21.15	$21.20
Purchase #6	$76.67	8.278%	$83.0167	$83.02	$83.00	$83.00
Purchase #7	$74.83	7.721%	$80.6076	$80.61	$80.60	$80.60
7 purchase totals =	$714.37		$766.5699	$766.56	$766.50	$766.50