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	$39.64	9.250%	$43.3067	$43.31	$43.30	$43.30
Purchase #2	$194.54	5.427%	$205.0977	$205.10	$205.10	$205.10
Purchase #3	$148.91	10.221%	$164.1301	$164.13	$164.15	$164.10
Purchase #4	$19.52	13.490%	$22.1532	$22.15	$22.15	$22.20
Purchase #5	$197.57	3.168%	$203.829	$203.83	$203.85	$203.80
Purchase #6	$157.73	9.372%	$172.5125	$172.51	$172.50	$172.50
Purchase #7	$213.45	12.693%	$240.5432	$240.54	$240.55	$240.50
7 purchase totals =	$971.36		$1,051.5724	$1,051.57	$1,051.60	$1,051.50