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	$158.31	9.383%	$173.1642	$173.16	$173.15	$173.20
Purchase #2	$232.92	9.154%	$254.2415	$254.24	$254.25	$254.20
Purchase #3	$55.31	7.619%	$59.5241	$59.52	$59.50	$59.50
Purchase #4	$243.55	8.861%	$265.131	$265.13	$265.15	$265.10
Purchase #5	$107.85	4.119%	$112.2923	$112.29	$112.30	$112.30
Purchase #6	$157.48	5.691%	$166.4422	$166.44	$166.45	$166.40
Purchase #7	$126.57	11.573%	$141.2179	$141.22	$141.20	$141.20
7 purchase totals =	$1,081.99		$1,172.0132	$1,172.00	$1,172.00	$1,171.90