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	$106.68	4.657%	$111.6481	$111.65	$111.65	$111.60
Purchase #2	$204.71	6.726%	$218.4788	$218.48	$218.50	$218.50
Purchase #3	$114.48	4.667%	$119.8228	$119.82	$119.80	$119.80
Purchase #4	$7.73	9.111%	$8.4343	$8.43	$8.45	$8.40
Purchase #5	$11.96	4.365%	$12.4821	$12.48	$12.50	$12.50
Purchase #6	$220.66	12.440%	$248.1101	$248.11	$248.10	$248.10
Purchase #7	$176.93	13.322%	$200.5006	$200.50	$200.50	$200.50
7 purchase totals =	$843.15		$919.4768	$919.47	$919.50	$919.40