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	$155.89	5.346%	$164.2239	$164.22	$164.20	$164.20
Purchase #2	$98.96	12.331%	$111.1628	$111.16	$111.15	$111.20
Purchase #3	$111.64	4.554%	$116.7241	$116.72	$116.70	$116.70
Purchase #4	$239.78	9.334%	$262.1611	$262.16	$262.15	$262.20
Purchase #5	$176.84	6.612%	$188.5327	$188.53	$188.55	$188.50
Purchase #6	$12.42	8.373%	$13.4599	$13.46	$13.45	$13.50
Purchase #7	$90.47	8.463%	$98.1265	$98.13	$98.15	$98.10
7 purchase totals =	$886.00		$954.3910	$954.38	$954.35	$954.40