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	$13.52	7.572%	$14.5437	$14.54	$14.55	$14.50
Purchase #2	$207.49	10.736%	$229.7661	$229.77	$229.75	$229.80
Purchase #3	$148.30	13.238%	$167.932	$167.93	$167.95	$167.90
Purchase #4	$144.85	10.866%	$160.5894	$160.59	$160.60	$160.60
Purchase #5	$95.45	4.662%	$99.8999	$99.90	$99.90	$99.90
Purchase #6	$187.63	4.800%	$196.6362	$196.64	$196.65	$196.60
Purchase #7	$247.90	3.825%	$257.3822	$257.38	$257.40	$257.40
7 purchase totals =	$1,045.14		$1,126.7495	$1,126.75	$1,126.80	$1,126.70