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	$114.96	10.597%	$127.1423	$127.14	$127.15	$127.10
Purchase #2	$229.89	7.240%	$246.534	$246.53	$246.55	$246.50
Purchase #3	$163.29	13.659%	$185.5938	$185.59	$185.60	$185.60
Purchase #4	$74.68	7.719%	$80.4445	$80.44	$80.45	$80.40
Purchase #5	$188.91	12.144%	$211.8512	$211.85	$211.85	$211.90
Purchase #6	$64.94	13.231%	$73.5322	$73.53	$73.55	$73.50
Purchase #7	$121.65	10.237%	$134.1033	$134.10	$134.10	$134.10
7 purchase totals =	$958.32		$1,059.2013	$1,059.18	$1,059.25	$1,059.10