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	$114.48	11.503%	$127.6486	$127.65	$127.65	$127.60
Purchase #2	$143.38	10.231%	$158.0492	$158.05	$158.05	$158.00
Purchase #3	$83.56	8.107%	$90.3342	$90.33	$90.35	$90.30
Purchase #4	$223.25	5.553%	$235.6471	$235.65	$235.65	$235.60
Purchase #5	$32.82	13.396%	$37.2166	$37.22	$37.20	$37.20
Purchase #6	$81.96	7.863%	$88.4045	$88.40	$88.40	$88.40
Purchase #7	$5.51	8.428%	$5.9744	$5.97	$5.95	$6.00
7 purchase totals =	$684.96		$743.2746	$743.27	$743.25	$743.10