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	$186.29	5.673%	$196.8582	$196.86	$196.85	$196.90
Purchase #2	$102.90	10.356%	$113.5563	$113.56	$113.55	$113.60
Purchase #3	$112.51	5.723%	$118.9489	$118.95	$118.95	$118.90
Purchase #4	$188.61	13.428%	$213.9366	$213.94	$213.95	$213.90
Purchase #5	$132.58	10.223%	$146.1337	$146.13	$146.15	$146.10
Purchase #6	$169.88	3.814%	$176.3592	$176.36	$176.35	$176.40
Purchase #7	$70.84	4.187%	$73.8061	$73.81	$73.80	$73.80
7 purchase totals =	$963.61		$1,039.5990	$1,039.61	$1,039.60	$1,039.60