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	$10.55	5.280%	$11.107	$11.11	$11.10	$11.10
Purchase #2	$12.38	9.426%	$13.5469	$13.55	$13.55	$13.50
Purchase #3	$226.47	13.153%	$256.2576	$256.26	$256.25	$256.30
Purchase #4	$157.40	3.493%	$162.898	$162.90	$162.90	$162.90
Purchase #5	$204.25	7.611%	$219.7955	$219.80	$219.80	$219.80
Purchase #6	$56.77	5.325%	$59.793	$59.79	$59.80	$59.80
Purchase #7	$118.90	7.610%	$127.9483	$127.95	$127.95	$127.90
7 purchase totals =	$786.72		$851.3463	$851.36	$851.35	$851.30