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	$212.39	3.821%	$220.5054	$220.51	$220.50	$220.50
Purchase #2	$148.62	3.660%	$154.0595	$154.06	$154.05	$154.10
Purchase #3	$142.42	7.626%	$153.2809	$153.28	$153.30	$153.30
Purchase #4	$27.57	13.602%	$31.3201	$31.32	$31.30	$31.30
Purchase #5	$106.90	11.845%	$119.5623	$119.56	$119.55	$119.60
Purchase #6	$100.33	5.560%	$105.9083	$105.91	$105.90	$105.90
Purchase #7	$207.46	6.158%	$220.2354	$220.24	$220.25	$220.20
7 purchase totals =	$945.69		$1,004.8719	$1,004.88	$1,004.85	$1,004.90