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	$159.92	4.465%	$167.0604	$167.06	$167.05	$167.10
Purchase #2	$193.74	13.571%	$220.0325	$220.03	$220.05	$220.00
Purchase #3	$199.69	5.631%	$210.9345	$210.93	$210.95	$210.90
Purchase #4	$111.34	11.236%	$123.8502	$123.85	$123.85	$123.90
Purchase #5	$226.93	10.649%	$251.0958	$251.10	$251.10	$251.10
Purchase #6	$10.29	5.807%	$10.8875	$10.89	$10.90	$10.90
Purchase #7	$103.82	11.333%	$115.5859	$115.59	$115.60	$115.60
7 purchase totals =	$1,005.73		$1,099.4468	$1,099.45	$1,099.50	$1,099.50