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	$40.40	9.839%	$44.375	$44.38	$44.40	$44.40
Purchase #2	$142.39	13.471%	$161.5714	$161.57	$161.55	$161.60
Purchase #3	$131.49	10.588%	$145.4122	$145.41	$145.40	$145.40
Purchase #4	$128.39	13.404%	$145.5994	$145.60	$145.60	$145.60
Purchase #5	$185.88	4.516%	$194.2743	$194.27	$194.25	$194.30
Purchase #6	$172.46	6.420%	$183.5319	$183.53	$183.55	$183.50
Purchase #7	$197.90	5.854%	$209.4851	$209.49	$209.50	$209.50
7 purchase totals =	$998.91		$1,084.2493	$1,084.25	$1,084.25	$1,084.30