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	$56.26	8.338%	$60.951	$60.95	$60.95	$61.00
Purchase #2	$45.90	9.254%	$50.1476	$50.15	$50.15	$50.10
Purchase #3	$167.61	10.543%	$185.2811	$185.28	$185.30	$185.30
Purchase #4	$108.39	4.671%	$113.4529	$113.45	$113.45	$113.50
Purchase #5	$130.29	6.779%	$139.1224	$139.12	$139.10	$139.10
Purchase #6	$144.35	9.648%	$158.2769	$158.28	$158.30	$158.30
Purchase #7	$190.44	3.152%	$196.4427	$196.44	$196.45	$196.40
7 purchase totals =	$843.24		$903.6746	$903.67	$903.70	$903.70