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	$154.76	8.810%	$168.3944	$168.39	$168.40	$168.40
Purchase #2	$38.68	9.417%	$42.3225	$42.32	$42.30	$42.30
Purchase #3	$111.68	12.541%	$125.6858	$125.69	$125.70	$125.70
Purchase #4	$59.84	4.508%	$62.5376	$62.54	$62.55	$62.50
Purchase #5	$174.98	8.873%	$190.506	$190.51	$190.50	$190.50
Purchase #6	$221.77	6.667%	$236.5554	$236.56	$236.55	$236.60
Purchase #7	$176.43	6.384%	$187.6933	$187.69	$187.70	$187.70
7 purchase totals =	$938.14		$1,013.6950	$1,013.70	$1,013.70	$1,013.70