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	$240.38	8.415%	$260.608	$260.61	$260.60	$260.60
Purchase #2	$143.39	11.187%	$159.431	$159.43	$159.45	$159.40
Purchase #3	$218.92	10.364%	$241.6089	$241.61	$241.60	$241.60
Purchase #4	$100.42	9.317%	$109.7761	$109.78	$109.80	$109.80
Purchase #5	$8.25	5.375%	$8.6934	$8.69	$8.70	$8.70
Purchase #6	$134.38	8.339%	$145.5859	$145.59	$145.60	$145.60
Purchase #7	$163.82	4.456%	$171.1198	$171.12	$171.10	$171.10
7 purchase totals =	$1,009.56		$1,096.8231	$1,096.83	$1,096.85	$1,096.80