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	$35.83	6.243%	$38.0669	$38.07	$38.05	$38.10
Purchase #2	$245.54	8.661%	$266.8062	$266.81	$266.80	$266.80
Purchase #3	$97.89	8.388%	$106.101	$106.10	$106.10	$106.10
Purchase #4	$94.40	11.590%	$105.341	$105.34	$105.35	$105.30
Purchase #5	$151.52	10.731%	$167.7796	$167.78	$167.80	$167.80
Purchase #6	$135.58	10.649%	$150.0179	$150.02	$150.00	$150.00
Purchase #7	$164.90	9.461%	$180.5012	$180.50	$180.50	$180.50
7 purchase totals =	$925.66		$1,014.6138	$1,014.62	$1,014.60	$1,014.60