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	$205.47	13.820%	$233.866	$233.87	$233.85	$233.90
Purchase #2	$56.56	3.538%	$58.5611	$58.56	$58.55	$58.60
Purchase #3	$158.88	5.415%	$167.4834	$167.48	$167.50	$167.50
Purchase #4	$232.72	12.698%	$262.2708	$262.27	$262.25	$262.30
Purchase #5	$117.44	13.334%	$133.0994	$133.10	$133.10	$133.10
Purchase #6	$76.46	12.411%	$85.9495	$85.95	$85.95	$85.90
Purchase #7	$122.53	12.204%	$137.4836	$137.48	$137.50	$137.50
7 purchase totals =	$970.06		$1,078.7138	$1,078.71	$1,078.70	$1,078.80