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	$177.78	9.546%	$194.7509	$194.75	$194.75	$194.80
Purchase #2	$202.96	10.827%	$224.9345	$224.93	$224.95	$224.90
Purchase #3	$158.71	13.488%	$180.1168	$180.12	$180.10	$180.10
Purchase #4	$106.74	4.278%	$111.3063	$111.31	$111.30	$111.30
Purchase #5	$210.67	12.297%	$236.5761	$236.58	$236.60	$236.60
Purchase #6	$45.84	13.192%	$51.8872	$51.89	$51.90	$51.90
Purchase #7	$156.39	10.535%	$172.8657	$172.87	$172.85	$172.90
7 purchase totals =	$1,059.09		$1,172.4375	$1,172.45	$1,172.45	$1,172.50