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	$149.71	7.572%	$161.046	$161.05	$161.05	$161.00
Purchase #2	$208.94	5.618%	$220.6782	$220.68	$220.70	$220.70
Purchase #3	$142.52	6.354%	$151.5757	$151.58	$151.60	$151.60
Purchase #4	$143.66	5.403%	$151.4219	$151.42	$151.40	$151.40
Purchase #5	$241.62	13.340%	$273.8521	$273.85	$273.85	$273.90
Purchase #6	$41.41	3.518%	$42.8668	$42.87	$42.85	$42.90
Purchase #7	$147.89	12.196%	$165.9267	$165.93	$165.95	$165.90
7 purchase totals =	$1,075.75		$1,167.3674	$1,167.38	$1,167.40	$1,167.40