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	$164.46	9.195%	$179.5821	$179.58	$179.60	$179.60
Purchase #2	$41.78	9.607%	$45.7938	$45.79	$45.80	$45.80
Purchase #3	$130.59	12.821%	$147.3329	$147.33	$147.35	$147.30
Purchase #4	$193.28	12.598%	$217.6294	$217.63	$217.65	$217.60
Purchase #5	$244.78	13.672%	$278.2463	$278.25	$278.25	$278.20
Purchase #6	$111.69	8.658%	$121.3601	$121.36	$121.35	$121.40
Purchase #7	$57.50	3.617%	$59.5798	$59.58	$59.60	$59.60
7 purchase totals =	$944.08		$1,049.5244	$1,049.52	$1,049.60	$1,049.50