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	$177.99	11.225%	$197.9694	$197.97	$197.95	$198.00
Purchase #2	$54.50	13.505%	$61.8602	$61.86	$61.85	$61.90
Purchase #3	$133.69	8.116%	$144.5403	$144.54	$144.55	$144.50
Purchase #4	$23.58	4.269%	$24.5866	$24.59	$24.60	$24.60
Purchase #5	$164.30	6.265%	$174.5934	$174.59	$174.60	$174.60
Purchase #6	$67.51	4.361%	$70.4541	$70.45	$70.45	$70.50
Purchase #7	$114.85	3.133%	$118.4483	$118.45	$118.45	$118.40
7 purchase totals =	$736.42		$792.4523	$792.45	$792.45	$792.50