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	$212.53	6.473%	$226.2871	$226.29	$226.30	$226.30
Purchase #2	$240.72	6.127%	$255.4689	$255.47	$255.45	$255.50
Purchase #3	$123.42	3.486%	$127.7224	$127.72	$127.70	$127.70
Purchase #4	$177.58	9.343%	$194.1713	$194.17	$194.15	$194.20
Purchase #5	$113.58	7.116%	$121.6624	$121.66	$121.65	$121.70
Purchase #6	$118.67	6.315%	$126.164	$126.16	$126.15	$126.20
Purchase #7	$31.73	5.404%	$33.4447	$33.44	$33.45	$33.40
7 purchase totals =	$1,018.23		$1,084.9208	$1,084.91	$1,084.85	$1,085.00