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	$113.30	5.465%	$119.4918	$119.49	$119.50	$119.50
Purchase #2	$249.88	11.257%	$278.009	$278.01	$278.00	$278.00
Purchase #3	$197.42	6.167%	$209.5949	$209.59	$209.60	$209.60
Purchase #4	$94.83	3.534%	$98.1813	$98.18	$98.20	$98.20
Purchase #5	$50.64	10.235%	$55.823	$55.82	$55.80	$55.80
Purchase #6	$9.65	6.409%	$10.2685	$10.27	$10.25	$10.30
Purchase #7	$85.65	4.452%	$89.4631	$89.46	$89.45	$89.50
7 purchase totals =	$801.37		$860.8316	$860.82	$860.80	$860.90