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	$242.29	8.261%	$262.3056	$262.31	$262.30	$262.30
Purchase #2	$130.47	11.647%	$145.6658	$145.67	$145.65	$145.70
Purchase #3	$140.77	9.872%	$154.6668	$154.67	$154.65	$154.70
Purchase #4	$142.81	6.548%	$152.1612	$152.16	$152.15	$152.20
Purchase #5	$16.44	12.429%	$18.4833	$18.48	$18.50	$18.50
Purchase #6	$117.60	12.145%	$131.8825	$131.88	$131.90	$131.90
Purchase #7	$192.39	7.158%	$206.1613	$206.16	$206.15	$206.20
7 purchase totals =	$982.77		$1,071.3265	$1,071.33	$1,071.30	$1,071.50