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	$186.50	5.565%	$196.8787	$196.88	$196.90	$196.90
Purchase #2	$96.33	4.768%	$100.923	$100.92	$100.90	$100.90
Purchase #3	$19.64	11.629%	$21.9239	$21.92	$21.90	$21.90
Purchase #4	$224.26	5.386%	$236.3386	$236.34	$236.35	$236.30
Purchase #5	$145.80	8.778%	$158.5983	$158.60	$158.60	$158.60
Purchase #6	$38.90	10.187%	$42.8627	$42.86	$42.85	$42.90
Purchase #7	$190.79	8.657%	$207.3067	$207.31	$207.30	$207.30
7 purchase totals =	$902.22		$964.8319	$964.83	$964.80	$964.80