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	$118.92	11.393%	$132.4686	$132.47	$132.45	$132.50
Purchase #2	$165.38	8.267%	$179.052	$179.05	$179.05	$179.10
Purchase #3	$155.71	13.118%	$176.136	$176.14	$176.15	$176.10
Purchase #4	$219.43	4.589%	$229.4996	$229.50	$229.50	$229.50
Purchase #5	$245.29	12.473%	$275.885	$275.89	$275.90	$275.90
Purchase #6	$141.28	3.169%	$145.7572	$145.76	$145.75	$145.80
Purchase #7	$236.82	7.819%	$255.337	$255.34	$255.35	$255.30
7 purchase totals =	$1,282.83		$1,394.1354	$1,394.15	$1,394.15	$1,394.20