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	$178.82	12.293%	$200.8023	$200.80	$200.80	$200.80
Purchase #2	$192.91	9.298%	$210.8468	$210.85	$210.85	$210.80
Purchase #3	$117.35	4.790%	$122.9711	$122.97	$122.95	$123.00
Purchase #4	$79.26	7.322%	$85.0634	$85.06	$85.05	$85.10
Purchase #5	$38.37	5.168%	$40.353	$40.35	$40.35	$40.40
Purchase #6	$145.59	6.730%	$155.3882	$155.39	$155.40	$155.40
Purchase #7	$235.61	12.697%	$265.5254	$265.53	$265.55	$265.50
7 purchase totals =	$987.91		$1,080.9502	$1,080.95	$1,080.95	$1,081.00