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	$12.78	13.592%	$14.5171	$14.52	$14.50	$14.50
Purchase #2	$83.26	8.603%	$90.4229	$90.42	$90.40	$90.40
Purchase #3	$246.80	6.812%	$263.612	$263.61	$263.60	$263.60
Purchase #4	$36.26	11.370%	$40.3828	$40.38	$40.40	$40.40
Purchase #5	$217.44	13.372%	$246.5161	$246.52	$246.50	$246.50
Purchase #6	$139.34	6.696%	$148.6702	$148.67	$148.65	$148.70
Purchase #7	$247.84	13.818%	$282.0865	$282.09	$282.10	$282.10
7 purchase totals =	$983.72		$1,086.2076	$1,086.21	$1,086.15	$1,086.20