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	$156.98	3.496%	$162.468	$162.47	$162.45	$162.50
Purchase #2	$177.35	7.627%	$190.8765	$190.88	$190.90	$190.90
Purchase #3	$20.48	12.786%	$23.0986	$23.10	$23.10	$23.10
Purchase #4	$214.71	3.750%	$222.7616	$222.76	$222.75	$222.80
Purchase #5	$42.89	11.624%	$47.8755	$47.88	$47.90	$47.90
Purchase #6	$244.73	11.274%	$272.3209	$272.32	$272.30	$272.30
Purchase #7	$141.88	11.871%	$158.7226	$158.72	$158.70	$158.70
7 purchase totals =	$999.02		$1,078.1237	$1,078.13	$1,078.10	$1,078.20