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	$217.85	5.132%	$229.0301	$229.03	$229.05	$229.00
Purchase #2	$242.63	12.217%	$272.2721	$272.27	$272.25	$272.30
Purchase #3	$20.84	3.751%	$21.6217	$21.62	$21.60	$21.60
Purchase #4	$112.98	3.156%	$116.5456	$116.55	$116.55	$116.50
Purchase #5	$45.59	13.134%	$51.5778	$51.58	$51.60	$51.60
Purchase #6	$161.35	7.853%	$174.0208	$174.02	$174.00	$174.00
Purchase #7	$42.51	6.685%	$45.3518	$45.35	$45.35	$45.40
7 purchase totals =	$843.75		$910.4199	$910.42	$910.40	$910.40