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	$162.64	3.313%	$168.0283	$168.03	$168.05	$168.00
Purchase #2	$155.60	5.867%	$164.7291	$164.73	$164.75	$164.70
Purchase #3	$43.30	4.331%	$45.1753	$45.18	$45.20	$45.20
Purchase #4	$229.26	13.234%	$259.6003	$259.60	$259.60	$259.60
Purchase #5	$56.32	11.108%	$62.576	$62.58	$62.60	$62.60
Purchase #6	$71.74	9.400%	$78.4836	$78.48	$78.50	$78.50
Purchase #7	$163.64	13.780%	$186.1896	$186.19	$186.20	$186.20
7 purchase totals =	$882.50		$964.7822	$964.79	$964.90	$964.80