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	$185.54	11.688%	$207.2259	$207.23	$207.25	$207.20
Purchase #2	$179.62	10.419%	$198.3346	$198.33	$198.35	$198.30
Purchase #3	$84.72	12.710%	$95.4879	$95.49	$95.50	$95.50
Purchase #4	$113.65	4.238%	$118.4665	$118.47	$118.45	$118.50
Purchase #5	$150.72	8.131%	$162.975	$162.98	$163.00	$163.00
Purchase #6	$233.78	3.789%	$242.6379	$242.64	$242.65	$242.60
Purchase #7	$127.52	13.266%	$144.4368	$144.44	$144.45	$144.40
7 purchase totals =	$1,075.55		$1,169.5646	$1,169.58	$1,169.65	$1,169.50