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	$143.69	9.299%	$157.0517	$157.05	$157.05	$157.10
Purchase #2	$118.56	10.850%	$131.4238	$131.42	$131.40	$131.40
Purchase #3	$99.69	12.226%	$111.8781	$111.88	$111.90	$111.90
Purchase #4	$222.43	11.602%	$248.2363	$248.24	$248.25	$248.20
Purchase #5	$23.46	3.614%	$24.3078	$24.31	$24.30	$24.30
Purchase #6	$193.41	9.370%	$211.5325	$211.53	$211.55	$211.50
Purchase #7	$121.98	8.341%	$132.1544	$132.15	$132.15	$132.20
7 purchase totals =	$923.22		$1,016.5846	$1,016.58	$1,016.60	$1,016.60