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	$167.96	12.701%	$189.2926	$189.29	$189.30	$189.30
Purchase #2	$168.89	12.826%	$190.5518	$190.55	$190.55	$190.60
Purchase #3	$113.35	12.798%	$127.8565	$127.86	$127.85	$127.90
Purchase #4	$170.84	4.833%	$179.0967	$179.10	$179.10	$179.10
Purchase #5	$91.79	3.425%	$94.9338	$94.93	$94.95	$94.90
Purchase #6	$169.52	10.509%	$187.3349	$187.33	$187.35	$187.30
Purchase #7	$192.26	5.852%	$203.5111	$203.51	$203.50	$203.50
7 purchase totals =	$1,074.61		$1,172.5774	$1,172.57	$1,172.60	$1,172.60