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	$179.82	11.352%	$200.2332	$200.23	$200.25	$200.20
Purchase #2	$100.29	6.741%	$107.0505	$107.05	$107.05	$107.10
Purchase #3	$148.82	3.668%	$154.2787	$154.28	$154.30	$154.30
Purchase #4	$125.59	13.479%	$142.5183	$142.52	$142.50	$142.50
Purchase #5	$120.30	9.854%	$132.1544	$132.15	$132.15	$132.20
Purchase #6	$67.27	4.313%	$70.1714	$70.17	$70.15	$70.20
Purchase #7	$164.82	6.126%	$174.9169	$174.92	$174.90	$174.90
7 purchase totals =	$906.91		$981.3234	$981.32	$981.30	$981.40