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	$171.96	3.252%	$177.5521	$177.55	$177.55	$177.60
Purchase #2	$193.98	12.604%	$218.4292	$218.43	$218.45	$218.40
Purchase #3	$131.60	10.837%	$145.8615	$145.86	$145.85	$145.90
Purchase #4	$204.40	11.180%	$227.2519	$227.25	$227.25	$227.30
Purchase #5	$128.26	11.168%	$142.5841	$142.58	$142.60	$142.60
Purchase #6	$169.86	12.296%	$190.746	$190.75	$190.75	$190.70
Purchase #7	$67.67	4.209%	$70.5182	$70.52	$70.50	$70.50
7 purchase totals =	$1,067.73		$1,172.9430	$1,172.94	$1,172.95	$1,173.00