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	$101.91	12.622%	$114.7731	$114.77	$114.75	$114.80
Purchase #2	$154.57	4.501%	$161.5272	$161.53	$161.55	$161.50
Purchase #3	$206.36	13.341%	$233.8905	$233.89	$233.90	$233.90
Purchase #4	$49.79	13.210%	$56.3673	$56.37	$56.35	$56.40
Purchase #5	$167.86	5.204%	$176.5954	$176.60	$176.60	$176.60
Purchase #6	$200.45	6.700%	$213.8802	$213.88	$213.90	$213.90
Purchase #7	$104.44	6.527%	$111.2568	$111.26	$111.25	$111.30
7 purchase totals =	$985.38		$1,068.2905	$1,068.30	$1,068.30	$1,068.40