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	$241.86	8.400%	$262.1762	$262.18	$262.20	$262.20
Purchase #2	$57.51	3.152%	$59.3227	$59.32	$59.30	$59.30
Purchase #3	$206.38	11.635%	$230.3923	$230.39	$230.40	$230.40
Purchase #4	$247.51	13.873%	$281.8471	$281.85	$281.85	$281.80
Purchase #5	$25.61	7.808%	$27.6096	$27.61	$27.60	$27.60
Purchase #6	$203.42	10.148%	$224.0631	$224.06	$224.05	$224.10
Purchase #7	$170.49	11.663%	$190.3742	$190.37	$190.35	$190.40
7 purchase totals =	$1,152.78		$1,275.7852	$1,275.78	$1,275.75	$1,275.80