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	$157.36	5.313%	$165.7205	$165.72	$165.70	$165.70
Purchase #2	$119.31	6.808%	$127.4326	$127.43	$127.45	$127.40
Purchase #3	$215.49	9.753%	$236.5067	$236.51	$236.50	$236.50
Purchase #4	$73.78	11.268%	$82.0935	$82.09	$82.10	$82.10
Purchase #5	$24.50	3.228%	$25.2909	$25.29	$25.30	$25.30
Purchase #6	$104.25	13.480%	$118.3029	$118.30	$118.30	$118.30
Purchase #7	$171.41	4.301%	$178.7823	$178.78	$178.80	$178.80
7 purchase totals =	$866.10		$934.1294	$934.12	$934.15	$934.10