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	$117.25	5.420%	$123.605	$123.61	$123.60	$123.60
Purchase #2	$34.52	11.529%	$38.4998	$38.50	$38.50	$38.50
Purchase #3	$143.59	10.148%	$158.1615	$158.16	$158.15	$158.20
Purchase #4	$171.88	13.182%	$194.5372	$194.54	$194.55	$194.50
Purchase #5	$94.88	9.275%	$103.6801	$103.68	$103.70	$103.70
Purchase #6	$73.91	8.258%	$80.0135	$80.01	$80.00	$80.00
Purchase #7	$162.85	4.297%	$169.8477	$169.85	$169.85	$169.80
7 purchase totals =	$798.88		$868.3448	$868.35	$868.35	$868.30