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	$115.88	9.243%	$126.5908	$126.59	$126.60	$126.60
Purchase #2	$127.54	11.251%	$141.8895	$141.89	$141.90	$141.90
Purchase #3	$143.65	13.110%	$162.4825	$162.48	$162.50	$162.50
Purchase #4	$92.45	10.692%	$102.3348	$102.33	$102.35	$102.30
Purchase #5	$217.65	9.624%	$238.5966	$238.60	$238.60	$238.60
Purchase #6	$95.29	13.683%	$108.3285	$108.33	$108.35	$108.30
Purchase #7	$103.61	11.322%	$115.3407	$115.34	$115.35	$115.30
7 purchase totals =	$896.07		$995.5634	$995.56	$995.65	$995.50