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	$99.80	11.773%	$111.5495	$111.55	$111.55	$111.50
Purchase #2	$48.76	10.373%	$53.8179	$53.82	$53.80	$53.80
Purchase #3	$200.95	6.616%	$214.2449	$214.24	$214.25	$214.20
Purchase #4	$201.53	6.123%	$213.8697	$213.87	$213.85	$213.90
Purchase #5	$84.61	10.589%	$93.5694	$93.57	$93.55	$93.60
Purchase #6	$216.68	11.356%	$241.2862	$241.29	$241.30	$241.30
Purchase #7	$102.70	8.284%	$111.2077	$111.21	$111.20	$111.20
7 purchase totals =	$955.03		$1,039.5453	$1,039.55	$1,039.50	$1,039.50