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	$55.86	3.299%	$57.7028	$57.70	$57.70	$57.70
Purchase #2	$107.42	6.492%	$114.3937	$114.39	$114.40	$114.40
Purchase #3	$129.77	13.188%	$146.8841	$146.88	$146.90	$146.90
Purchase #4	$220.77	9.579%	$241.9176	$241.92	$241.90	$241.90
Purchase #5	$113.93	11.193%	$126.6822	$126.68	$126.70	$126.70
Purchase #6	$210.26	4.396%	$219.503	$219.50	$219.50	$219.50
Purchase #7	$105.42	3.684%	$109.3037	$109.30	$109.30	$109.30
7 purchase totals =	$943.43		$1,016.3871	$1,016.37	$1,016.40	$1,016.40