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	$12.38	10.606%	$13.693	$13.69	$13.70	$13.70
Purchase #2	$173.86	12.388%	$195.3978	$195.40	$195.40	$195.40
Purchase #3	$233.26	3.412%	$241.2188	$241.22	$241.20	$241.20
Purchase #4	$39.89	6.289%	$42.3987	$42.40	$42.40	$42.40
Purchase #5	$85.64	5.422%	$90.2834	$90.28	$90.30	$90.30
Purchase #6	$88.29	9.792%	$96.9354	$96.94	$96.95	$96.90
Purchase #7	$244.79	7.139%	$262.2656	$262.27	$262.25	$262.30
7 purchase totals =	$878.11		$942.1927	$942.20	$942.20	$942.20